upd

ZeroLevel/Services/Network/FileTransfer/FileReader.cs

@@ -45,8 +45,7 @@ namespace ZeroLevel.Network.FileTransfer
                     offset = offset + 1;
                     yield return fragment;
                 }
-            }
+            }            
-            GC.Collect();
         }
 
         public FileEndFrame GetCompleteInfo()

ZeroLevel/Services/Network/FileTransfer/FileSender.cs

@@ -123,6 +123,7 @@ namespace ZeroLevel.Network.FileTransfer
                 }
             }
             Send(task.Client, "__file_transfer_complete_transfer__", reader.GetCompleteInfo(), _resendWhenClientError, _resendWhenServerError);
+            GC.Collect();
         }
     }
 }