Rockyboy, I had the same problem till I did the following.
With dbpoweramp if you are choosing different cover art than they auto picked you have to delete all other art so there is only 1 picture you picked. It looks like only the 1st picture is saved.
With dbpoweramp if you are choosing different cover art than they auto picked you have to delete all other art so there is only 1 picture you picked. It looks like only the 1st picture is saved.