Crash on Mac when attempting to Join Sessions

User reporting crash on his Mac. He seemed to have narrowed down the reproduction to attempting to join a multiplayer session.

"After the crashes when I restart UE4 and open my project some BPs are not correctly compiled. They are errors that some functions of other classes are not there. The error vanishes when I just go into that class and recompile it. Mostly I am not able anymore to join sessions."

Link to CrashReporter

[Link Removed]

Repro steps unknown.

UE4Editor-OpenGLDrv.dylib!FOpenGLViewport::~FOpenGLViewport()
UE4Editor-OpenGLDrv.dylib!FOpenGLViewport::~FOpenGLViewport()
UE4Editor-SlateRHIRenderer.dylib!FRHIResource::Release()
UE4Editor-SlateRHIRenderer.dylib!FSlateRHIRenderer::FViewportInfo::~FViewportInfo()
UE4Editor-SlateRHIRenderer.dylib!FSlateRHIRenderer::FViewportInfo::~FViewportInfo()
UE4Editor-SlateRHIRenderer.dylib!FSlateRHIRenderer::OnWindowDestroyed(TSharedRef<SWindow,()
UE4Editor-Slate.dylib!FSlateApplication::PrivateDestroyWindow(TSharedRef<SWindow,()
UE4Editor-Slate.dylib!FSlateApplication::DestroyWindowsImmediately()
UE4Editor-Slate.dylib!FSlateApplication::RequestDestroyWindow(TSharedRef<SWindow,()
UE4Editor-Slate.dylib!FSlateApplication::DestroyWindowImmediately(TSharedRef<SWindow,()
UE4Editor-UnrealEd.dylib!UEditorEngine::TeardownPlaySession()
UE4Editor-UnrealEd.dylib!UEditorEngine::EndPlayMap()
UE4Editor-UnrealEd.dylib!UEditorEngine::Tick()
UE4Editor-UnrealEd.dylib!UUnrealEdEngine::Tick()
UE4Editor!FEngineLoop::Tick()
UE4Editor!GuardedMain()
UE4Editor!<Unknown>
UE4Editor-Core.dylib!<Unknown>
Foundation!<Unknown>
libsystem_pthread.dylib!<Unknown>
libsystem_pthread.dylib!<Unknown>
libsystem_pthread.dylib!<Unknown>