Errors after upgrade: Playback strange and notes missing from score

I recently upgraded to the following version:
OS: Windows 10 (10.0), Arch.: x86_64, MuseScore version (64-bit): 3.5.0.13199, revision: 43c5553

A score I had been working on (attached) has gone totally crazy. Most seriously, some notes have disappeared from the score, but strangely can still be heard on the playback. Other notes are rendered correctly but played incorrectly by the playback feature (ties on some notes are being ignored and the note sounds twice).

Reopennig the score did not help, neither did reentering the notes.

I have not checked whether any of my other scores have been affected as I don't dare to open them until this issue is resolved.