As I have "isolated" the bug I edit my first post and title for clarity:
There is a glitch with how Plex handle smart playlist filtered by the track rating.
All my smart playlist that have a filter with track rating are not working on iOS: I have them synced but I can not open them (infinite rotating wheel).
I have found that the songs are not the cause as I can listen to the same song in a regular synced playlist
I can also listen to the smart playlist when streamed
Smart playlist that do not have track rating filter are fine too.
I just rebuilded a new plex server from the ground up on a dedicated i7 PC.
After importing all my media and analysed them I synced some smart playlist (> 4* and > 2*) to my phone.
The sync starts but always finish with errors (on the same songs but those songs are perfectly fine and playable thru Plex web and in streaming).
I tried with a different quality setting so they get reencoded but same issue.
This could be okay as it is only few songs but then, on iOS I select my "phone server" to get the synced playlist, and there is just an infinite rotating wheel (loading) for local synced playlist (it never loads).
--> If I select my server and the same playlist on the same phone, it loads fine and I am able to listen to all music in streaming.
At the end, the only way to listen to my music is to stream as I am completely unable to sync.
I tried to delete and reinstall the app, no change.
Running on iOS 10.3.1 no jailbreak or whatsover.
Pictures of the issue: imgur.com/a/5YhyV
1st : infinite loading when I try to access a synced playlist
2nd : Errors that I have when I try to sync playlists.
Edited by sa2000 to make links visible as links