game crashes at random when more that 2 people are playing. the more people the more often it crashes. we are using the steam subsystem, I do not know if that will have anything to do with it or not.
here is the crash log
Assertion failed: IsInGameThread() || IsAsyncLoading() [File:D:\Build++UE4+Release-4.15+Compile\Sync\Engine\Source\Runtime\Engine\Private\Materials\MaterialInstance.cpp] [Line: 465]
KERNELBASE.dll!0x00000000BB119E08
PS_TPS.exe!FOutputDeviceWindowsError::Serialize()
PS_TPS.exe!FOutputDevice::Logf__VA()
PS_TPS.exe!FDebug::AssertFailed()
PS_TPS.exe!UMaterialInstance::GetMaterial()
PS_TPS.exe!UMaterialInterface::GetRelevance()
PS_TPS.exe!FParticleEmitterInstance::GatherMaterialRelevance()
PS_TPS.exe!UParticleSystemComponent::CacheViewRelevanceFlags()
PS_TPS.exe!UParticleSystemComponent::CreateSceneProxy()
PS_TPS.exe!FScene::AddPrimitive()
PS_TPS.exe!FScene::UpdatePrimitiveTransform()
PS_TPS.exe!UPrimitiveComponent::SendRenderTransform_Concurrent()
PS_TPS.exe!UParticleSystemComponent::SendRenderTransform_Concurrent()
PS_TPS.exe!UActorComponent::DoDeferredRenderUpdates_Concurrent()
PS_TPS.exe!TActorIteratorBase >::operator++()
PS_TPS.exe!FParallelForData::Process()
PS_TPS.exe!TGraphTask::ExecuteTask()
PS_TPS.exe!FTaskThreadAnyThread::ProcessTasks()
PS_TPS.exe!FTaskThreadAnyThread::ProcessTasksUntilQuit()
PS_TPS.exe!FTaskThreadBase::Run()
PS_TPS.exe!FRunnableThreadWin::Run()
PS_TPS.exe!FRunnableThreadWin::GuardedRun()
KERNEL32.DLL!0x00000000BC362774
ntdll.dll!0x00000000BE020D51
ntdll.dll!0x00000000BE020D51
Crash in runnable thread TaskGraphThreadNP 1
any help would be greatly appreciated