Fix/reset default app / "open with"

I have a Samsung Galaxy S21 android phone, android 12. There has been an issue with playing music from dropbox for many months now. I can't get my old preferred default music player back. If I just play a song from dropbox it opens in this player by default: When I open a song by longpress and choosing "open with" it opens my beloved and preferred music player overlay: It doesn't show a list of apps to choose from and there are no other music player apps installed on the phone. There is no option to choose "always". If I try installing a third-party music player for test, THEN the "open with" shows a list of players including the old preferred default app (white overlay player). But no matter what I choose and go "open with, ALWAYS", my choice is being ignored onward and it opens this player again: I have tried doing a reset of app settings on the phone, no change. I wish to have my old good default music player back ;) Any suggestions or help is appreciated.