i realized that Dianemo is double tagging mp3s.
i am using an external windows software for tagging the files.
if i - e.g. add an correctly tagged album to dianemo it looks ok.
If i change something for example Album to something else externally, than dianemo resyncs it, but adds the new album as a second album tag in each file. So the album tag is existing 2 times. and the album is existing two times.
Same is for all other tags.