Plex does not support AC4 audio, the format used in ATSC 3.0 broadcasts. If you record a program, it will have no audio.
See this thread (which also mentions EPG issues): ATSC3.0 Broadcast and AC-4 Sound
Regarding EPG Errors:
See this thread: Reporting Plex DVR Lineup Inaccuracies
Then post to this thread: Live TV EPG - The update you’ve been waiting for
