I tried to upgrade our Bartender environment from R7  to R8 and after the upgrade the Integration service would not start again. 

Application error:

Faulting application name: Integration.Service.exe, version: 11.3.209.432, time stamp: 0x64fc0583
Faulting module name: unknown, version: 0.0.0.0, time stamp: 0x00000000
Exception code: 0xc0000005
Fault offset: 0x00007ffbdcdfb5ca
Faulting process id: 0x1ce0
Faulting application start time: 0x01db7c8dae163fa2
Faulting application path: C:\Program Files\Seagull\BarTender 2022\Integration.Service.exe
Faulting module path: unknown
Report Id: 8f588c89-d944-421c-85de-2ca212af7ef0
Faulting package full name: 
Faulting package-relative application ID: 

.Net Runtime:

Application: Integration.Service.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.AccessViolationException
   at <Module>.gcroot<Seagull::Interop::IOnAsyncDataReceived ^>..PE$AAUIOnAsyncDataReceived@Interop@Seagull@@(gcroot<Seagull::Interop::IOnAsyncDataReceived ^>*)
   at <Module>.Seagull.Interop.AsyncFileReader.FileIOCompletionRoutine(UInt32, UInt32, _OVERLAPPED*)
   at System.Threading.Thread.SleepInternal(Int32)
   at System.Threading.ReaderWriterLockSlim.SpinWait(Int32)
   at System.Threading.ReaderWriterLockSlim.TryEnterWriteLockCore(TimeoutTracker)
   at System.Threading.ReaderWriterLockSlim.TryEnterWriteLock(TimeoutTracker)
   at System.ServiceModel.Channels.SharedConnectionListener+SharedListenerProxy.OnControlChannelShutdown()
   at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.InputSessionDoneReceivingCore(System.ServiceModel.Channels.ServiceChannel)
   at System.ServiceModel.Channels.ServiceChannel.HandleReceiveComplete(System.ServiceModel.Channels.RequestContext)
   at System.ServiceModel.Dispatcher.ChannelHandler.HandleReceiveComplete(System.ServiceModel.Channels.RequestContext)
   at System.ServiceModel.Dispatcher.ChannelHandler.EndTryReceive(System.IAsyncResult, System.ServiceModel.Channels.RequestContext ByRef)
   at System.ServiceModel.Dispatcher.ChannelHandler.AsyncMessagePump(System.IAsyncResult)
   at System.ServiceModel.Dispatcher.ChannelHandler.OnAsyncReceiveComplete(System.IAsyncResult)
   at System.Runtime.Fx+AsyncThunk.UnhandledExceptionFrame(System.IAsyncResult)
   at System.Runtime.AsyncResult.Complete(Boolean)
   at System.ServiceModel.Channels.TransportDuplexSessionChannel+TryReceiveAsyncResult.OnReceive(System.IAsyncResult)
   at System.Runtime.Fx+AsyncThunk.UnhandledExceptionFrame(System.IAsyncResult)
   at System.Runtime.AsyncResult.Complete(Boolean)
   at System.ServiceModel.Channels.SynchronizedMessageSource+ReceiveAsyncResult.OnReceiveComplete(System.Object)
   at System.ServiceModel.Channels.SessionConnectionReader.OnAsyncReadComplete(System.Object)
   at System.ServiceModel.Channels.PipeConnection.OnAsyncReadComplete(Boolean, Int32, Int32)
   at System.ServiceModel.Channels.OverlappedContext.CompleteCallback(UInt32, UInt32, System.Threading.NativeOverlapped*)
   at System.Runtime.Fx+IOCompletionThunk.UnhandledExceptionFrame(UInt32, UInt32, System.Threading.NativeOverlapped*)
   at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32, UInt32, System.Threading.NativeOverlapped*)