I live in the UK, I’ve just upgraded my plex recording from a single to a dual WinTVHD Tuner. Since this I have found that many of the movies I go to record come up as only being 60mins (somtimes 65mins) long. It doesnt do it for all movies just some.
You could try re-analyzing the files to see if the run time changes. Maybe Plex looked at them before they were done.
Another possibility is bad signal quality may produce corrupted timing info in the file. I get that all the time here - sole transmitter was hit by lighting 5 years ago and that really didn’t do it any good. Sometimes 30 minute shows report they are 190 hours in length… when they say that they’re unwatchable tho.
If you’re using HDHR equipment there’s a handy (really handy) free phone app (not developed by SDust) that’ll inspect your tuners reporting all types of happy info.
Your phone is a HECK of a lot easier to carry onto the roof than your desktop.
Also - with HDHR equipment, you can employ the little known, seldom used signal inspector program that exists somewhere in the HDHR engine’s folder structure (pretty easy to find). They don’t expose that to the public at large for some reason, but it works a treat.