Corrupted measures
In musescore 3 you could ask for details when the score would not open due to corrupted measures. One could write down the measures and correct them. Can you do that in musescore 4...there is no 'details' button in the error notice.
Comments
Known and reported numerous times before. It is supposed to come back in a later release
Meanwhile, see:
https://musescore.org/en/node/341420#comment-1163408
which explains how to use the MuseScore 3 'details' button by opening a MuseScore 4 .mscx (uncompressed) file in MuseScore 3 and therein enumerate the corrupted measures for repair.