I found the root of the problem ... I have a Timer with 1/100th of second to update the display, if I set the timer to 1 second everything works. I need to detect the status of the app to check if it enters in background and change the timer frequency accordingly.
ruribe
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Here it is : https://apps.apple.com/us/genre/ios/id36
I'm facing the same problem ... do you find any solution?
Thanks.