You're right, I'll try to be more detailed.
Following your last suggestion, I tried to compile the tag "albumartist" in order to check if the stereo read that tag instead of the tag "artist", but the problem recurs.
As mentioned, the strange thing is that this problem occurs only with certain artists (perhaps little known) that have names similar to other existing artists (Feder becomes Feeder or Federico Stragà become Federico Scavo for example) and the stereo automatically renames them.
To tell the truth, I noticed this thing also with other artists, whose names have been corrected by the stereo if they were written in a wrong way by me (my stereo does not give me "Royksopp" as I wrote in all the tags, but "Rӧyksopp" that is in fact the correct name). It is as if my stereo were linked to a database automatically. I think this also because, despite having eliminated all the covers, pictures of the artists quite always appear on the stereo. I do not know if my assumption may be correct.
I thank you for your patience and support. I really hope to solve this little problem, it is a shame to see artists' names wrong on the stereo.