Musescore randomly starts ignoring the time signature

It's probably been 2 or 3 days now that, randomly, Musescore will completely go haywire.

Take for example, Twinkle Twinkle:

C C G G | A A G | F F E E | D D C etc.

Up until a few days ago, the next phrase would be entered (and display) exactly normally:

G G F F | E E D | G G F F | E E D etc.

But now randomly, without warning, Musescore is deciding to expand the size of the bar (in practice, but without formally changing the time signature, so it looks something like

G G F F E E D G G F F E E D C C G G | A A G F F E E D D C

Both of those "bars" are much longer than 4 beats, but... that's the problem.

In certain situations (famously, the Allegri Miserere), this kind of unmetered notation is good/required, but in Twinkle Twinkle, in what I'm actually writing, and in almost all other cases, this is a terribly annoying bug.

There's no way to predict when this glitch will engage, and no way to stop it other than rebooting once it does. And once the glitch engages, there's no predictability as to how long these super-bars will be, before Musescore decides to put in a bar line.

And this morning, I lost a file (which I recovered thanks to my backups) that I had been working on for a year, once Musescore realized it had done that to itself, and then basically told me "oops sorry the file is corrupted!"

Can anyone help me either find a way to stop this myself, or put me in contact with the developers so I can report this bug and get a timeline on a fix ASAP?