Starting game now crashes with Assertion failed

I have the project setup for c++ compiling etc, mostly for dedicated server builds, the project has no c++ actors added or anything, its a BP only project. Debugging in VS breaks at the same line (563) inside this function:

void UBlueprintGeneratedClass::InitPropertiesFromCustomList(uint8* DataPtr, const uint8* DefaultDataPtr)
{
	FScopeLock SerializeAndPostLoadLock(&SerializeAndPostLoadCritical);
	check(bCustomPropertyListForPostConstructionInitialized); // Something went wrong, probably a race condition

	if (const FCustomPropertyListNode* CustomPropertyList = GetCustomPropertyListForPostConstruction())
	{
		InitPropertiesFromCustomList(CustomPropertyList, this, DataPtr, DefaultDataPtr);
	}
}

Im going to look into reproducing this in a new project, the main project is pretty large so not sure I can isolate the issue without any further debug info from VS, it seems pretty much anything could have failed that assert.