Failed to load/save savegame file for some (not all) players (UE, Quest 2 issue)

Hi,

Most of our players savegame progress files are saved and loaded correctly, but in rare cases there is an error with loading/saving these files to the Oculus Quest 2 device (as reported to us by players themselves).

We have connected the Game Analytics service and verified that some players have an error with reading / writing savegame files to the device. We have already tried to reproduce the bug, but on our device this problem did not occur in either the developer build or the shipping build (we tested it on Oculus Quest 2 device).

Additional information:
- we use Unreal Engine 4.27.2
- "Use ExternalFilesDir for UE4Game files?" is enabled
- TargetSDKVersion=32
- According to VRC.Quest.Security.2 we do not use the READ_EXTERNAL_STORAGE and WRITE_EXTERNAL_STORAGE permissions in the Android manifest file, as the Oculus page says "Not needed for savegames" (https://developer.oculus.com/resources/vrc-quest-security-2/). Despite this, we tried requesting these permissions from the player at runtime, they accepted, but that didn't solve the problem for them either.

Has anyone experienced this? What could be the cause of this weird bug?