Save button always greyed out even after changes

I have just loaded a large amount of files into mp3tag and was making some changes when I noticed I could not save and that the save button was greyed out. If I try to leave the track that I have made changes to in the Tag Panel, MP3Tag will ask if I want to save the changes, but that is the only way I can execute the save. If I click on the save button or hit CTRL+S nothing happens. Any ideas why this is happening?

Which MP3tag version? 3.25b does not show that behaviour over here.
What kind of files?
Does it also happen with a single file loaded?
Which user-id (the same that installed MP3tag) sees this behaviour?

It was in 3.25, but I upgraded and restarted and things are working fine now.