Changing effective measure length behaves erratically (and Undo doesn't properly Undo)

Dear Musescore enthusiasts,

I discovered a strange behaviour when changing the effective length of a measure in Musescore 4.0.1.

Here is a simple example:

Now I change the effective length of the second measure to 17/16, because I want to add an extra 16th. What I get is this:
Not quite what I wanted: the first quarter of the next measure is gone and there is an extra 16th there. Huh?

Now what's more weird is this: I press Undo (Ctrl+Z) and I get this:
What? The third bar is missing a quarter entirely!

I save the file and reload and I get this:
Okay, it's gone but I can at least reinsert that.

What's worse: I recently did this in a more complex score and it really ruined the measure after the score (and Undo didn't undo it). And: saving the file and reloading told me that now the file is corrupt!

I hope this can be fixed as in my world, Undo should always Undo whatever I just messed up :)