A track doesn't get the mp3 labels

On a ripped cd of 20 tracks I try to add a number of labels. I select them all and type the composer name and try to save it. At track 13 MP3TAG gives a message that it couldn't write write to that rack.
All tracks have the same properties, 19 tracks get the correct labels like composer. Only track 13 fails to write.
What is wrong and how to solve this?

see e.g. here:

In that thread more threads are linked, see them as well.