Unreal 4.27 Development Build causes steamdeck to freeze when triggering ensureMsgf

[Eko-Stairwaygames]

Proton version: 9.0-3
Game: Coral Island
AppId: 1158160
Engine: Unreal 4.27

We encounter issue where the steamdeck would freeze and be unresponsive. Even pressing the power button does not make the steam deck sleeps. We have to force the steamdeck to turn off.

We only encounter this issue recently, we have been testing on steamdeck for months now. We suspect it is caused by 9.0-3 update.

We narrow it down to when the game would throw an ensureMsgf.
Shipping build with the same codebase does not have the issue.
Interestingly the steamdeck do not freeze when triggering the ensureMsgf while we attached remote debugging session.

Forcing the proton version back to 8.0-5 seems to solve the freezing issue. But it is not ideal since the player base need to apply it manually.