the "recommdation" didn't broke anything, i removed it again and system is running as expected.
BUT, the umlaut problem was never working since i am using dianemo. Long time ago we fixed it in linuxmce.
i am tagging my mp3 - because of the hughiness - outside of dianemo.
In Germany and some other european countries we got some characters, like the german umlaut or french accents etc. If the UpdateMedia finds such a file, it is imported, but the ä ö ü is converted to some other character.
surely it is about the character set. The encoding of the mp3 tags in the files it utf-8 or utf-16.
Furthermore, sometimes after updating tags outside of dianemo (and linuxmce), when e.g. the album title was changed (from bla bla to blabla extended edition), updatemedia seems to save both of the albumtitels to the mp3 (or database), same for performer, and titel.
I know that isn't always a bug, but wanted, in case there are various performer, but in case of album titel and titel, it doesn' make sense at all for me.