AVAssetExportSession never starts on older devices, device needs to be rebooted

问题

On iPhone 7 and iPadPro 9.7, running iOS 14.3, the AVAssetExportSession never starts exporting when calling exportSession.exportAsynchronously, it simply appears to be stuck with no error messages describing what is wrong.

If we reboot those devices, and run exportSession.exportAsynchronously, then the export starts immediately and completes successfully.

The issue does not occur on my iPhone 12 Pro.

It appears to be a bug in iOS 14.3 as is reported at the below link. But, I cannot find the explanation anywhere.

Swift - AVAssetExportSession exportSession.exportAsynchronously completion handler not called

Can anyone offer an explanation as to why the reboot makes the app work?

Thanks,

来源：https://stackoverflow.com/questions/65576443/avassetexportsession-never-starts-on-older-devices-device-needs-to-be-rebooted