Right hand fingering style for guitar

A few days ago I upgraded from MuseScore v.2 to v.3, and have since been trying to understand how stylesheets work in version 3, specifically with respect to fingering settings for guitar. As for left hand fingering, everything seems to be working in the same way as in the previous version. However, with respect to right hand fingering, the system seems to behave erratically (unless I'm missing something completely ;-) ).

For example, see the first example where initially RH fingering was put close to the notes and on the legato line. After manually moving the first occurrence of "m" above the line and saving the document, it stays in the same place after re-opening the file. However, for some strange reason, the other fingering settings often revert to the default setting. Often, not always.

Any idea as to what I'm doing wrong?

Thanks in advance for any advice or suggestions.