Critical crash caused by gRPC thread – "Pure virtual function being called

Unreal Engine Bugs
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1

Hi,
I am getting a consistent crash in Unreal Engine 5 when Convai is active. The project runs, but on closing PIE or exiting a level, the engine throws:

Fatal error:
Pure virtual function being called
[File: D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Private\Windows\WindowsPlatformMisc.cpp] [Line: 769]

In the log I also see:

Runnable thread gRPC_Stub crashed.
Crash in runnable thread gRPC_Stub

This indicates that the Convai gRPC background thread is still calling into an object after destruction or during shutdown.

Relevant log section:

Message: Pure virtual function being called while application was running (GIsRunning == 1).
LogThreadingWindows: Error: Runnable thread gRPC_Stub crashed.
LogWindows: Error: Crash in runnable thread gRPC_Stub

The crash only happens when Convai is involved. Without Convai enabled, the project closes correctly and no thread errors appear.

I need information on:

  • How to properly stop Convai’s gRPC thread before shutdown or level unload

  • Whether there is a known patch or fix for this issue

  • Any recommended workaround to prevent callbacks after Actor/UObject destruction

I am available to share full logs and project details if needed.

Thanks.

2

We have unfortunately not been able to reproduce this crash on our side so far. For now, my recommendation is to try our Unreal Engine Beta plugin.

https://docs.convai.com/api-docs/plugins-and-integrations/unreal-engine-plugin-beta-overview/installation-and-setup