Engine Crash on RepLayout.cpp (using blueprints only)

Development Programming & Scripting Blueprint
1

Hi, we upgraded the engine from 4.18.1 to 4.18.2 and now we are having a crash when trying to test multiplayer behavior by opening two PIE windows.
Game starts, client connect to server, but when we start to load some blueprints that have rep-notify variables on it, the game crash.

If we open the same project on 4.18.1, everything just works fine.

log file:

LogWindows: Error: === Critical error: ===
[2018.01.12-17.56.44:159][529]LogWindows: Error:
[2018.01.12-17.56.44:159][529]LogWindows: Error: Assertion failed: Parents*.Property->RepIndex + Parents*.ArrayIndex == i [File:D:\Build++UE4+Release-4.18+Compile\Sync\Engine\Source\Runtime\Engine\Private\RepLayout.cpp] [Line: 2980]
[2018.01.12-17.56.44:159][529]LogWindows: Error:
[2018.01.12-17.56.44:159][529]LogWindows: Error:
[2018.01.12-17.56.44:159][529]LogWindows: Error:
[2018.01.12-17.56.44:159][529]LogWindows: Error: [Callstack] 0x00000000D4303FB8 KERNELBASE.dll!UnknownFunction ]
[2018.01.12-17.56.44:159][529]LogWindows: Error: [Callstack] 0x00000000C47376D4 UE4Editor-ApplicationCore.dll!UnknownFunction ]
[2018.01.12-17.56.44:159][529]LogWindows: Error: [Callstack] 0x00000000AA5F330B UE4Editor-Core.dll!UnknownFunction ]
[2018.01.12-17.56.44:159][529]LogWindows: Error: [Callstack] 0x00000000AA5847F9 UE4Editor-Core.dll!UnknownFunction ]
[2018.01.12-17.56.44:159][529]LogWindows: Error: [Callstack] 0x00000000A5000C53 UE4Editor-Engine.dll!UnknownFunction ]
[2018.01.12-17.56.44:159][529]LogWindows: Error: [Callstack] 0x00000000A4D49349 UE4Editor-Engine.dll!UnknownFunction ]
[2018.01.12-17.56.44:159][529]LogWindows: Error: [Callstack] 0x00000000A4D427A5 UE4Editor-Engine.dll!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000A4260CFD UE4Editor-Engine.dll!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000A4D73CFC UE4Editor-Engine.dll!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000A4D719E6 UE4Editor-Engine.dll!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000A4D7B4F5 UE4Editor-Engine.dll!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000A4D4065F UE4Editor-Engine.dll!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000A419CF78 UE4Editor-Engine.dll!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000A4BE858D UE4Editor-Engine.dll!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000A7D96BA6 UE4Editor-UnrealEd.dll!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000A8644AC6 UE4Editor-UnrealEd.dll!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000EE415A26 UE4Editor.exe!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000EE425430 UE4Editor.exe!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000EE4254AA UE4Editor.exe!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000EE432379 UE4Editor.exe!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000EE433D57 UE4Editor.exe!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000D61E1FE4 KERNEL32.DLL!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000D717EFB1 ntdll.dll!UnknownFunction ]
[2018.01.12-17.56.44:160][529]LogWindows: Error: [Callstack] 0x00000000D717EFB1 ntdll.dll!UnknownFunction ]

Its possible to revert the engine version ? is this a know bug for 4.18.2 ?

2

Hey,

Following up on my problem, we found that if we recompile every blueprint that have a rep-notify variable on it, we can successfully run multiplayer with two PIE windows.
We need to do this every time the editor restart, otherwise, the editor will crash.

If we test multiplayer behavior using two computers and running the game in standalone mode, we don’t have this issue (probably because the game is build from zero).

If we disconnect EVERY rep-notify variable and restart the editor, the game STILL crash, meaning that our rep-notify functions are not causing the issue. But if we recompile the blueprints, the game will run without problems.

For testing propose, we created a blank third person template project, declared a boolean rep-notify variable on the third person character, that execute a very simple function, and no problems were observed when running PIE mode with two windows. So we are clueless on why our project is behaving like this.