Bug during managing separate parts

I wrote a piece for 4 guitars but in editing separate parts the program created 3 more parts which are duplicates of the 'real' 4 parts. I thought that maybe I could have done an error in duplicating manually some parts, but it couldn't be because if you do that the program let you delete alle the extra part you created, while in this case the extra parts are considered as 'real' parts so they couldn't be deleted.
I have to report also that while I was trying to fix this issue the program crashed several times (I can't remember the exact number, but it happened at least 3 or 4 times)
Thank you for all you do, I trust you will be able to fix this bug.

P.S. I gave different names to the 'extra' parts you can see displayed in the Parts window to let you know to which 'real' part they refer to, and also to make order and manage to continue working on the score. The first time I opened that window all the parts had the same name: "Chitarra Classica"