beamer v3.60 with a fix for this issue was released on 14 Dec. 2020 and is available now in MikTeX and TeX Live. The problem should disappear if you thoroughly update your TeX system.
The workaround shown below is no longer needed and should be removed.
This was a timing issue with
The problem was reported at https://github.com/josephwright/beamer/issues/625 and fixed in https://github.com/josephwright/beamer/pull/626.
beamer version (v3.60?) hasn't been released yet, though. If you need a fix now, you can use the following temporary workaround suggested by samcarter in https://github.com/josephwright/beamer/issues/625
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