iTunes tags have disappeared from songs not bought in iTunes

A dance teacher colleague who uses Algoriddim's DJay software and iTunes has found that all the tags (comments) she created have suddenly disappeared for any tracks not purchased through iTunes.

My understanding is that DJay doesn't allow you to create or store tags, it just uses the tags created in iTunes. So the issue seems to be with iTunes.

Please can anyone help advise why these tags have disappeared from iTunes and how she can get them back.

She's not using Catalina, so probably using Mojave.

Many thanks for any suggestions.