I have a smart playlist for soundtrack that is set to only show tracks rated 3 or above not played in the last 4 months, which is synced to my phone. It’s limited to 4 hours of music.
Played tracks are not removed from the downloads in PlexAmp, even though when loading the playlist in the Plex client (or even PlexAmp), the tracks that have been played are indeed filtered out. I have a similar playlist for my non-soundtrack music, which works just fine. Played tracks are removed, and replaced by other tracks on refresh.
The only difference I can see between the two situations is that the soundtrack playlist currently does not have enough tracks to fill the 4 hour limit restriction for PlexAmp’s sync settings, while the non-soundtrack playlist has excess tracks. However I have seen the non-soundtrack playlist “empty itself” when I was playing lots of music and eventually end up empty when all tracks had been played within the 4 months and eventually refill itself as tracks were re-added after the expected time had passed - so why is the soundtrack playlist not doing this?
Screenshots of the playlist filters (not sure if helpful, seeing as they actually work as intended in Plex.

