Found issue both on S20 Note Ultra and S25 Ultra. Whenever there is a track change, the music control in the notification drawer will show the last played song. Its until I skip or go back that it corrects itself, but repeats after song changes. this issue has been ongoing for years it seems like and looks to be unpatched. I have tried This step provided on Reddit but came with no results,
If, as the co-founder said, it’s an issue with the Samsung phone’s background restrictions, you can long press the app, go into Plexamp settings, and look around there