Just came across this post. I had this issue when I converted my iOS jukebox app to Mac Catalyst last year. I also discovered that changing the playback state would update playback time, so I added a play() command that is triggered in my one second Timer, and that solved my problem!

Yeah, I posted about it on Stack Overflow when I was stuck like you, and then answered my own question, including the code snippet I used. No weird side effects, the overhead is negligible, just have to remember you can’t control play/pause in Music while your app is in use. Glad you were able to get a fix from it, too!

Welp. As of Sonoma 14.6.x calling applicationMusicPlayer crashes the Music app. Using systemMusicPlayer was the only choice for my music player until upgrading to Sonoma, and now I must return to it again. So weird…