I have Plex on various iPhone 4, and 3GS's around the house and I can't get them to play music reliably. Songs will inevitably skip forward anytime from several seconds after to 30-60 seconds in the track. I used to not have this problem but I now an incompatibility.
The PMS is the latest version as of today. The Clients are running on whatever is the latest version for iOS 6(3GS) (Plex 18.104.22.168) and the iPhone 4 is running iOS 8 and has whatever is most recently compatible version for that.
I suspect the issue related to the various old iOS clients. I have no prob with all my iOS 10 Plex clients or with Plex web so who knows....
No amount of changing the direct play/direct streaming/universal transcoder/clearing of cache settings seems to help.
Any help would be appreciated!