Multiplayer Game crashes on one or more clients when there are at least 2 remote clients apart from the server

Development Programming & Scripting Multiplayer & Networking
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1

Hello,

when playtesting my packaged game in a LAN - multiplayer game, one or more of the remote clients always crash after entering the level. It only happens when there are at least 2 remote clients apart from the server player. One of the remote clients never crash.

Error Message:
Assertion failed: Src [File:D:/Build/++UE4/Sync/Engine/Source/Runtime/CoreUObject/Private/UObject/Class.cpp] [Line: 2496]

I have opened the Class.cpp in Visual Studio to see where the crash occurs and it appears to be in the CopyScriptStruct - function.

The reported line is a Macrofunction - call:

check(src)

My knowledge of Macros and the Unreal Engine is not sufficient to comprehend what it does. I haven’t found any place in the Unreal Code from where CopyScriptStruct is called, either.

I suspect that the cause of these crashes could be a bug in Engine. However, I wished I could get an idea of which things make the Engine call this code to get an idea of what makes it happen.

Currently the project contains mainly Blueprint with some functionality transferred over to C++. These crashes did not occur at an earlier point of development when the game used an older version of the Engine and it was 100% Blueprint. The Project uses the AdvancedSessions - plugin.

Any help would be greatly appreciated.

2

It turns out that I was using a struct from an actor which, on some clients, had not replicated yet.

I was passing the struct property from this invalid actor to a new actor for creation, resulting in this crash, since the input struct was accordingly invalid, like the actor from which it was retrieved.

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I’ll make sure to provide log files the next time I post a question like this.