I’ve just tested this by creating a track collection and I am able to add more than 400 tracks. Successfully adding more tracks on both Plex web and plexamp
Server Version 1.41.8.9834
Plex Web Version 4.146.0
Plexamp v4.12.3
So, it looks like you are using the newest beta version of PMS. I’ll give that a try. However, it’s strange how your Plex Web is a version behind 4.146.0 vs 4.147.0. We are using the same Plexamp version.
Oh boy, this gets more interesting (I have not installed any new patches)…
So, as a workaround I had converted the previous collection to a smart collection by adding a Genre Tag to all the tracks. I then used that new Genre Tag for the Smart Collection filter. This got me passed the 400 and to 407. I deleted the old non-smart collection.
Now, in order to test again, I went into the new Smart Collection and added all 407 tracks to a new non-smart collection. It worked! I then used Plex Web to add a new track and that took the non-smart collection to 408. Then used Plexamp to add another to 409.
I’m quite positive I couldn’t add more tracks when hitting 400 earlier. Well, now that I can’t recreate the problem I guess this thread will go nowhere. Strange.