A couple of MS4 weird behaviour

all starts from importing a MusicXML file, I'll list the commands to replicate the issues:
XML file was produced with StaffPad (that you should know well... )
I attached various versions of the file I obtained after each operation

My setup:
iMac (Retina 4K, 21.5-inch, Late 2015), 3,1 GHz Intel Core i5 quad-core
8 GB 1867 MHz DDR3, Intel Iris Pro Graphics 6200 1536 MB
OSX 12.6.2 (Monterey)

Now the problems:
1) Open the XML file
[attached: All my loving 3 voci.xml]

1st problem:

2) the score is imported but the chords don't show the name letters, only the quality (e.g. instead of 'Cm7' you see 'm7'). The chords play regularly though.
3) Save the imported file in *.mscz format, reopen it, and the chords display and play regularly.
[attached: AMLtest1.mscz]

2nd problem:
4) add a new instrument, Contrabass from the 'Strings - bowed' group. It will add a new staff using a soundfont file (all the other are Muse Sounds)
[attached: AMLtest2.mscz]

5) click on the 4/4 pause in the second measure and press 'F', to insert a 4/4 F note
** weird behaviour starts here **
I see MS repeatedly adding multiple notes of many lower octaves, like an 'alt+DNarrow' key combination was stuck.
You hear and see in the mixer some noise coming from the instrument channel
This happens also if I try to insert a note clicking with the mouse.
[attached AMLtest2.jpg]

6) Replace instrument to 'Strings - bowed / Contrabasses (section)'. A Muse Sound instrument is selected.
** now the 'F' insertion works regularly **
[attached: AMLtest3.mscz]

7) If you set the Soundfont contrabass again, the weird behaviour reappears.

Hope it helps