Tvheadend

I recently noticed that the reverse also happens: Finished Recordings reported 30 data errors for one recording while there were no CC errors in the log.

The numbers are different because they are measuring different things.

My understanding (please correct me if I'm wrong!) is that 'errors' and 'data errors' are derived from the tuner's device driver, and are caused by poor signal level, interference and so on. 'Continuity errors' are logged by Tvheadend and indicate that an entire TS data packet has been missed.

I don't think that's the case. Like I said: I've noticed more than once that the recording is OK according to the errors/data errors fields while the log contains CC errors. And the CC errors indeed show up when watching the recording.

If it helps: I'm only recording IPTV, i.e. udp traffic. So, no dvb devices involved.