[Troglodyte]

Well, thanks for the comment, but the first thing I did was of course to check the tags of the faulty files and everything checked.Below is a screen cap of the MP3Tag file
http://i.imgur.com/2Qv0apl.jpg
And here's the result after scrapping in Kodi
http://i.imgur.com/emcnnnR.jpg
Funny thing is, all the faulty files display belong to the album "Afterburner" and have the corresponding cover.
I cannot think of anything so help is very much welcome.
Thanks