I had to get Channels DVR because of this same problem. I still use plex for movies and music but not for OTA DVR. I had tried using Shedules Direct for data importing an .xmltv file using EPG123 but that now throws out junk and I Have to rescan manually every week.
I suspect Gracenote is the problem but what to do about that?
Maybe if we all complain at this address:
http://support.gracenote.com/articles/Public_FAQ/Questions-About-TV-Data-Guides/?l=en_US&c=Public%3AConsumers&cu=1&fs=ContactUs&pn=1
