Adding or removing measures when parts are defined doesn't work.

I will describe both problems together as I think they are closely related.

FIRST ISSUE: ADDING MEASURES IN A SCORE WITH PARTS CRASHES
How to reproduce.
1. I created a 4-parts score for our choir, with 2 staves (i.e. Soprano-Alto on the treble key, Tenor-Bass on the bass key).
2. I extracted 4 parts so I could export mp3 and midi files for each voice.
3. I noticed that I needed to add a few extra measures.
4. I did ctrl-Insert (to insert a few measures) and added 10 measures.
5. I am able to see the score with the extra measures added for 5 seconds, then Musescore crashes.
It's always reproducible.

Solution :
– Remove the parts.
– Save the score.
– Add the extra measures.

SECOND ISSUE : DELETING MEASURES AFTER THAT IS IMPOSSIBLE
How to reproduce.
I noticed that in the above work where I previously had parts, I had added 2 measures too many
1. Select measures and try to delete them with Ctrl-Delete or the menu
2. Nothing happens.

Solution :
– Save the score and quit Musescore
– Restart Musescore.
– Now it works correctly (i.e. I can add and remove measures without any problems),

SOFTWARE:
OS: Windows 10 (10.0) (French-Canadian), Arch.: x86_64, MuseScore version (64-bit): 3.4.1.9660, revision: 20414b2

OTHER INFORMATION

– Same problem happens (crash) if I change the time signature (ex.: 3/4 to 4/4) or do any other manipulations that change the number of measures.

– I can do the same (adding or removing measures ; changing time signature) in a score that has parts defined if I use Musescore 3.3.4.9066, revision: 7684abe

Below is one of the files I used for this experiment.