diff --git a/.github/ISSUE_TEMPLATE/create-new-issue.md b/.github/ISSUE_TEMPLATE/create-new-issue.md
deleted file mode 100644
index 7eefcd4..0000000
--- a/.github/ISSUE_TEMPLATE/create-new-issue.md
+++ /dev/null
@@ -1,38 +0,0 @@
----
-name: Create new issue
-about: Create a detailed issue to help us to fix them
-labels: 
-
----
-
-<!--- Provide a general summary of the issue in the Title above -->
-
-## Expected Behavior
-<!--- If you're describing a bug, tell us what should happen -->
-<!--- If you're suggesting a change/improvement, tell us how it should work -->
-
-## Current Behavior
-<!--- If describing a bug, tell us what happens instead of the expected behavior -->
-<!--- If suggesting a change/improvement, explain the difference from current behavior -->
-
-## Possible Solution
-<!--- Not obligatory, but suggest a fix/reason for the bug, -->
-<!--- or ideas how to implement:  the addition or change -->
-
-## Steps to Reproduce (for bugs)
-<!--- Provide a link to a live example, or an unambiguous set of steps to -->
-<!--- reproduce this bug. Include configuration, logs, etc. to reproduce, if relevant -->
-1.
-2.
-3.
-4.
-
-## Context
-<!--- How has this issue affected you? What are you trying to accomplish? -->
-<!--- Providing context helps us come up with a solution that is most useful in the real world -->
-
-## Your Environment
-<!--- Include as many relevant details about the environment you experienced the problem in -->
-* PowerShell Version used (`$PSVersionTable.PSVersion`):
-
-* Operating System and version (`Get-IcingaWindowsInformation Win32_OperatingSystem | Select-Object Version, BuildNumber, Caption`):
diff --git a/.gitignore b/.gitignore
index 732984e..273c546 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,6 +8,7 @@ cache/*
 *.log
 *.pfx
 *.dll
+*.DS_Store
 
 # JEA
 RoleCapabilities/IcingaForWindows.psrc
diff --git a/doc/100-General/10-Changelog.md b/doc/100-General/10-Changelog.md
index c5165dd..1e809dc 100644
--- a/doc/100-General/10-Changelog.md
+++ b/doc/100-General/10-Changelog.md
@@ -18,6 +18,7 @@ Released closed milestones can be found on [GitHub](https://github.com/Icinga/ic
 ### Bugfixes
 
 * [#673](https://github.com/Icinga/icinga-powershell-framework/pull/673) Fixes a memory leak while fetching Windows EventLog information by using CLI tools and inside the Hyper-V provide
+* [#678](https://github.com/Icinga/icinga-powershell-framework/pull/678) Fixes various memory leaks in Icinga for Windows API core and check handler
 
 ## 1.11.1 (2023-11-07)
 
diff --git a/lib/core/cache/Get-IcingaCacheData.psm1 b/lib/core/cache/Get-IcingaCacheData.psm1
index 27004fb..c38975b 100644
--- a/lib/core/cache/Get-IcingaCacheData.psm1
+++ b/lib/core/cache/Get-IcingaCacheData.psm1
@@ -33,7 +33,8 @@ function Get-IcingaCacheData()
         [string]$Space,
         [string]$CacheStore,
         [string]$KeyName,
-        [switch]$TempFile   = $FALSE
+        [switch]$TempFile   = $FALSE,
+        [switch]$AsObject   = $FALSE
     );
 
     $CacheFile       = Join-Path -Path (Join-Path -Path (Join-Path -Path (Get-IcingaCacheDir) -ChildPath $Space) -ChildPath $CacheStore) -ChildPath ([string]::Format('{0}.json', $KeyName));
@@ -62,7 +63,7 @@ function Get-IcingaCacheData()
         return $null;
     }
 
-    if ([string]::IsNullOrEmpty($KeyName)) {
+    if ($AsObject -Or [string]::IsNullOrEmpty($KeyName)) {
         return $cacheData;
     } else {
         return $cacheData.$KeyName;
diff --git a/lib/core/cache/Set-IcingaCacheData.psm1 b/lib/core/cache/Set-IcingaCacheData.psm1
index 09be2c3..cb0f0c8 100644
--- a/lib/core/cache/Set-IcingaCacheData.psm1
+++ b/lib/core/cache/Set-IcingaCacheData.psm1
@@ -43,7 +43,7 @@ function Set-IcingaCacheData()
     }
 
     if ((Test-Path $CacheFile)) {
-        $cacheData = Get-IcingaCacheData -Space $Space -CacheStore $CacheStore;
+        $cacheData = Get-IcingaCacheData -Space $Space -CacheStore $CacheStore -KeyName $KeyName -AsObject;
     } else {
         try {
             New-Item -ItemType File -Path $CacheTmpFile -Force -ErrorAction Stop | Out-Null;
diff --git a/lib/core/logging/Write-IcingaDebugMessage.psm1 b/lib/core/logging/Write-IcingaDebugMessage.psm1
index fbb2796..6489483 100644
--- a/lib/core/logging/Write-IcingaDebugMessage.psm1
+++ b/lib/core/logging/Write-IcingaDebugMessage.psm1
@@ -18,4 +18,6 @@ function Write-IcingaDebugMessage()
     $DebugContent += $Objects;
 
     Write-IcingaEventMessage -EventId 1000 -Namespace 'Debug' -ExceptionObject $ExceptionObject -Objects $DebugContent;
+
+    $DebugContent = $null;
 }
diff --git a/lib/daemons/RestAPI/client/Test-IcingaRESTClientConnection.psm1 b/lib/daemons/RestAPI/client/Test-IcingaRESTClientConnection.psm1
index 828902e..0690c5c 100644
--- a/lib/daemons/RestAPI/client/Test-IcingaRESTClientConnection.psm1
+++ b/lib/daemons/RestAPI/client/Test-IcingaRESTClientConnection.psm1
@@ -11,7 +11,7 @@ function Test-IcingaRESTClientConnection()
             -Client $Connection.Client `
             -ClientList $Global:Icinga.Public.Daemons.RESTApi.ClientBlacklist;
         Write-IcingaEventMessage -EventId 1501 -Namespace 'Framework' -Objects $Connection.Client.Client;
-        Close-IcingaTCPConnection -Client $Connection.Client;
+        Close-IcingaTCPConnection -Connection $Connection;
         $Connection = $null;
         return $FALSE;
     }
diff --git a/lib/daemons/RestAPI/daemon/New-IcingaForWindowsRESTApi.psm1 b/lib/daemons/RestAPI/daemon/New-IcingaForWindowsRESTApi.psm1
index f249e9a..247f6d2 100644
--- a/lib/daemons/RestAPI/daemon/New-IcingaForWindowsRESTApi.psm1
+++ b/lib/daemons/RestAPI/daemon/New-IcingaForWindowsRESTApi.psm1
@@ -84,9 +84,15 @@ function New-IcingaForWindowsRESTApi()
             -Client (New-IcingaTCPClient -Socket $Socket) `
             -Certificate $Certificate;
 
+        if ($Connection.Client -eq $null -Or $Connection.Stream -eq $null) {
+            Close-IcingaTCPConnection -Connection $Connection;
+            $Connection = $null;
+            continue;
+        }
+
         if (Test-IcingaRESTClientBlacklisted -Client $Connection.Client -ClientList $Global:Icinga.Public.Daemons.RESTApi.ClientBlacklist) {
             Write-IcingaDebugMessage -Message 'A remote client which is trying to connect was blacklisted' -Objects $Connection.Client.Client;
-            Close-IcingaTCPConnection -Client $Connection.Client;
+            Close-IcingaTCPConnection -Connection $Connection;
             $Connection = $null;
             continue;
         }
@@ -98,7 +104,7 @@ function New-IcingaForWindowsRESTApi()
 
         # API not yet ready
         if ($Global:Icinga.Public.Daemons.RESTApi.ApiRequests.Count -eq 0) {
-            Close-IcingaTCPConnection -Client $Connection.Client;
+            Close-IcingaTCPConnection -Connection $Connection;
             $Connection = $null;
             continue;
         }
@@ -107,7 +113,7 @@ function New-IcingaForWindowsRESTApi()
             $NextRESTApiThreadId = (Get-IcingaNextRESTApiThreadId);
 
             if ($Global:Icinga.Public.Daemons.RESTApi.ApiRequests.ContainsKey($NextRESTApiThreadId) -eq $FALSE) {
-                Close-IcingaTCPConnection -Client $Connection.Client;
+                Close-IcingaTCPConnection -Connection $Connection;
                 $Connection = $null;
                 continue;
             }
diff --git a/lib/daemons/RestAPI/threads/New-IcingaForWindowsRESTThread.psm1 b/lib/daemons/RestAPI/threads/New-IcingaForWindowsRESTThread.psm1
index d1656f4..6a7d7c8 100644
--- a/lib/daemons/RestAPI/threads/New-IcingaForWindowsRESTThread.psm1
+++ b/lib/daemons/RestAPI/threads/New-IcingaForWindowsRESTThread.psm1
@@ -38,7 +38,7 @@ function New-IcingaForWindowsRESTThread()
                         # Send the authentication prompt
                         Send-IcingaWebAuthMessage -Connection $Connection;
                         # Close the connection
-                        Close-IcingaTCPConnection -Client $Connection.Client;
+                        Close-IcingaTCPConnection -Connection $Connection;
                         $Connection = $null;
                         continue;
                     }
@@ -56,14 +56,14 @@ function New-IcingaForWindowsRESTThread()
                         # Re-send the authentication prompt
                         Send-IcingaWebAuthMessage -Connection $Connection;
                         # Close the connection
-                        Close-IcingaTCPConnection -Client $Connection.Client;
+                        Close-IcingaTCPConnection -Connection $Connection;
                         $Connection = $null;
                         continue;
                     }
                 }
 
                 # Set our thread being active
-                Set-IcingaForWindowsThreadAlive -ThreadName $Global:Icinga.Protected.ThreadName -Active -TerminateAction @{ 'Command' = 'Close-IcingaTCPConnection'; 'Arguments' = @{ 'Client' = $Connection.Client } };
+                Set-IcingaForWindowsThreadAlive -ThreadName $Global:Icinga.Protected.ThreadName -Active -TerminateAction @{ 'Command' = 'Close-IcingaTCPConnection'; 'Arguments' = @{ 'Connection' = $Connection } };
 
                 # We should remove clients from the blacklist who are sending valid requests
                 Remove-IcingaRESTClientBlacklist -Client $Connection.Client -ClientList $Global:Icinga.Public.Daemons.RESTApi.ClientBlacklist;
@@ -100,7 +100,7 @@ function New-IcingaForWindowsRESTThread()
 
         # Finally close the clients connection as we are done here and
         # ensure this thread will close by simply leaving the function
-        Close-IcingaTCPConnection -Client $Connection.Client;
+        Close-IcingaTCPConnection -Connection $Connection;
         $Connection = $null;
 
         # Force Icinga for Windows Garbage Collection
diff --git a/lib/icinga/plugin/New-IcingaCheckResult.psm1 b/lib/icinga/plugin/New-IcingaCheckResult.psm1
index ec9e293..ec4ce55 100644
--- a/lib/icinga/plugin/New-IcingaCheckResult.psm1
+++ b/lib/icinga/plugin/New-IcingaCheckResult.psm1
@@ -40,11 +40,17 @@ function New-IcingaCheckResult()
 
         Set-IcingaInternalPluginExitCode -ExitCode $ExitCode;
 
+        $this.Check = $null;
+
         return $ExitCode;
     }
 
     if ($Compile) {
-        return $IcingaCheckResult.Compile();
+        $IcingaExitCode    = $IcingaCheckResult.Compile();
+        $IcingaCheckResult = $null;
+        $Check             = $null;
+
+        return $IcingaExitCode;
     }
 
     return $IcingaCheckResult;
diff --git a/lib/webserver/Close-IcingaTCPConnection.psm1 b/lib/webserver/Close-IcingaTCPConnection.psm1
index 86beeae..d995ca2 100644
--- a/lib/webserver/Close-IcingaTCPConnection.psm1
+++ b/lib/webserver/Close-IcingaTCPConnection.psm1
@@ -1,21 +1,40 @@
 function Close-IcingaTCPConnection()
 {
     param(
-        [System.Net.Sockets.TcpClient]$Client = $null
+        [hashtable]$Connection = @{ }
     );
 
-    if ($null -eq $Client) {
+    if ($null -eq $Connection -Or $Connection.Count -eq 0) {
+        $Connection = $null;
+
         return;
     }
 
     Write-IcingaDebugMessage -Message (
         [string]::Format(
             'Closing client connection for endpoint {0}',
-            (Get-IcingaTCPClientRemoteEndpoint -Client $Client)
+            (Get-IcingaTCPClientRemoteEndpoint -Client $Connection.Client)
         )
     );
 
-    $Client.Close();
-    $Client.Dispose();
-    $Client = $null;
+    try {
+        if ($null -ne $Connection.Stream) {
+            $Connection.Stream.Close();
+            $Connection.Stream.Dispose();
+            $Connection.Stream = $null;
+        }
+    } catch {
+        $Connection.Stream = $null;
+    }
+    try {
+        if ($null -ne $Connection.Client) {
+            $Connection.Client.Close();
+            $Connection.Client.Dispose();
+            $Connection.Client = $null;
+        }
+    } catch {
+        $Connection.Client = $null;
+    }
+
+    $Connection = $null;
 }
diff --git a/lib/webserver/New-IcingaSSLStream.psm1 b/lib/webserver/New-IcingaSSLStream.psm1
index 05d13a0..12a1310 100644
--- a/lib/webserver/New-IcingaSSLStream.psm1
+++ b/lib/webserver/New-IcingaSSLStream.psm1
@@ -9,10 +9,17 @@ function New-IcingaSSLStream()
         return $null;
     }
 
+    [System.Net.Security.SslStream]$SSLStream = $null;
+
     try {
-        $SSLStream = New-Object System.Net.Security.SslStream($Client.GetStream(), $false)
+        $SSLStream = New-Object System.Net.Security.SslStream($Client.GetStream(), $false);
         $SSLStream.AuthenticateAsServer($Certificate, $false, [System.Security.Authentication.SslProtocols]::Tls12, $true) | Out-Null;
     } catch {
+        if ($null -ne $SSLStream) {
+            $SSLStream.Close();
+            $SSLStream.Dispose();
+            $SSLStream = $null;
+        }
         Write-IcingaEventMessage -EventId 1500 -Namespace 'Framework' -ExceptionObject $_ -Objects $Client.Client;
         return $null;
     }