If I rewind it and then start it it’s OK. Then I can pull the slider along on my iPad or iPhone to where I was up to then it works fine. Pretty sure it only started after I installed version 1.11.0.4666. Running this with my Chromecast wifi to my iMac. No other issues since the disappearing subtitles bug was fixed. Since my hearing is poor watch all shows with subs.
There is an bug with iOS devices: http://forums.plex.tv/discussion/302865/all-of-the-sudden-problems-with-playback-on-ios-devices#latest
It’s being worked on use work around suggested by sergious.