Maybe they should enable manual recordings that allow you to select a channel and time to record, like every other DVR software I have used in the last 20 years. This has been requested for years and ignored.
It appears to be too simple for Plex, but they need to accept that guide data is never going to be perfect (and it’s a long way short of that at the moment) and giving a simple work around would be useful to all their DVR customers.