Made an app specifically to test this error today.
It is a very simple, patch new line of data into a sharepoint list.
Tested a few different things by using it.
First I opened PowerApps on the Ipad and left it open for about 20 minutes.
Then I opened the App to test with which started a countdown timer (2HRS). Every 10 minutes I clicked the submit button with following code in it's OnClick
Patch(TESTPOWERAPPS,Defaults(TESTPOWERAPPS),{Title:"TEST",time:Now()})
Once the timer hit 1hr 20 minutes, the error everyone is mentioning occured.

At this point I hit the refresh button I added to test if it was correctable by an inapp refresh, it's onclick is
Refresh(TESTPOWERAPPS)
I then clicked submit again and recieved the same error.
Next step I closed the APP only (not whole powerapps prograM) via swipe, then reopened the app and tried submitting again. Same error message again.
Finally I closed the PowerApps program completely, reopened it, and loaded up the app and THIS let it submit.
SO in summary, about 1 HR after you open the powerapps program (not the apps within it) you will begin facing token issues.
I found 1 iPad that it does not occur on, an Ipad Pro, with a different iOs operating system version, so that may be another place to look for issues
See below
Broken Tokens
Tokens Work