iOS. Push notification from any app cause ue4 game freeze

iOS. Push notification from any app cause ue4 game freeze

How to reproduce:

  1. Build and run any UE4 (4.22 or 4.23) project on iOS 13
  2. Receive a notification during the game. Render thread will freeze

What will happen:

Receive a notification during the game developed on UE4. Render thread will freeze for a couple of seconds but the audio thread will work fine.

This leads to an out of sync image and sound, which is very bad for music games and critical for shooters!


Muted device doesn’t freeze by notifications (watch the video below)

This is a critical problem for us and our team began to search where else you can find the same bug.

And we found …

This is reproducible in any (??) UE4 project running at least on iOS 13. For example:

Appstore: FORTNITE, Oceanhorn 2, Action RPG, UnrealMatch3

Marketplace (after build): Action RPG, UnrealMatch3, FaceAR Sample

We recorded a video with UE4 games on two different devices running on iOS 13. [UE4 Development] Push notification from any app cause UE4 game freezing on iOS 13 - YouTube

Look at screenshot from UE4 profiler from iOS device. Each peak on the chart is the moment when a notification was displayed.

How can we fix this?


We’ve recently made a switch to a new bug reporting method using a more structured form. Please visit the link below for more details and report the issue using the new Bug Submission Form. Feel free to continue to use this thread for community discussion around the issue.