I have a couple of flac files and with some of them I have Problems. When I e.g. want to delete the Artist name, it appears again. When I write the artistname like "ExampleArtist" once and press return, the artistname appears as "ExampleArtist\\Exampleartist" Here is a picture of it:
Furthermore when I click extended tags I have multiple Artists, Albumnames etc.:
According to the contents of the topic mentioned above I have solved the problem using foobar 2000. Using foobar, I have been able to completely remove the tags from the flac files. Afterwards I could edit them as usual in mp3tag.