some tracks i record in via vinyl have no artwork, so i google the artwork, download the picture and click import cover in traktor.
But the next time i open tractor the artwork has gone.
I’ve also noticed this happens sometimes with beatgrids and locked tracks, i open it up and there will be the odd couple of tracks no longer locked and the beatgrid/cues not there.
I don’t normally use traktor to edit my MP3 metadata. If you are using a PC, I’d recommend Media Monkey. On Mac, I’ve always used itunes. Using those, I’ve never really run into that issue.