MuseScore crashes when pasting a fretboard diagram without chord symbol to a note/chord where already one fretboard diagram exists

Hallo Marc (and all other friends who cared about that problem),
first: apologies for me answering so late, You emails dropped into my Spam Folder, I realized the only yesterday ... but now I hat set musescore.org on my whitelist.
second: In case it might still be of use, I include the score, where I stumbled into the crash. I should have done this at once. I made all further tests with that score. feel free to tear it apart ...
third: I read the hints on your hint-links and yes, my crash problem seems to originate from what you already have found. It occurs only if you paste a previously copied fret diagram that hasn't been combined with a chord symbol. It's no matter if the element, it is pasted on, is a note or a pause or whether it has already some fret diagram or anything else attached to or whether it's bare. It comes down to simply pasting a previously copied (!) fret diagram without a chord symbol. If there are still other issues that may cause that crash - I did not come across them. I wasn't able to provoke the crash with a Bb7 diagram that I attached to a bare note right from out of the standard diagram template. That is obviously because it automatically brings along its chord symbol. However, after deleting the chord symbol (only that) from the staff and then copying & pasting that very diagram to another place I crashed again. As well I did NOT crash when copying a combined fret diagram plus chord symbol from the staff (not the templates) and pasting it elsewhere. As far as I've derived from all the hints JoJo-Schmitz has focussed on a Null-pointer reason and has resolved the issue in version 3.51. If so, thank you very much.
In case you want5 to play around with my score concentrate on measures 17 to 20 where two diagrams are attached to one note/pause. Meanwhile, I have realized, though, that the problem is NOT two diagrams attached to one note, BUT pasting a diagram without a combined chord symbol. I suppose that is is the case throughout the whole score. Alas, one can not immediately see if the chord symbol has been put along with the diagram or as a single element, one only realizes that, while moving the elements. It is already an older score of mine where I at first thought the chord symbols to be enough ant only later decided to add diagrams. If the brought along their own symbols I may have deleted them for they didn't fit after changing the fret and because I had already the correct one in the score. (this connects to my other issue 1021004 on automatically changing chord symbol root name when changing the diagram's fret).

fourth: thanks, for your by-the-way-hint to store individual diagrams in self-created templates. I did this rather extensively and created (for systematical reasons and to keep an overview) templates for extended major chords, extended dominant-sept chords, and extended minor chords - with the relevant diagrams in them. A very useful feature I am very grateful for! However, you can't in no way store diagrams for all possible chords there. Not even all different patterns of diagrams. You would get lost later on when searching for a certain diagram. Moreover, regarding extended chords you can often re-interpret them as different chords (symbols) depending on where you locate (or omit) the root tone - just think of an em7b5 = C7/9 = gm6 = Bb6#11 ...
Therefore there will always be a situation where you either move a basic pattern from the templates and edit it afterwards or copy a certain diagram from one place in the score to another place. In the context of a song's melody line, it is not unlikely, that a chord of rather an uncommon shape occurs several times as motives often are similar. Then it is most convenient to just copy & paste, isn't it?

In any case thanks a lot for your contributions
Michael Gimmel