It is related to your EPG setup. It looks like you've changed EPG sources at some point, from either 'none' (with manually created channel's), or DVB EPG, to XMLTV. The way its currently configured, only some combinations of channels can be recorded at the same time.
I'd delete your gbpvr.db3 file, start the config app and it'll create a new database, then set you capture sources up again from scratch, with xmltv as the epg source from the beginning. If you still have the problem after that (I'm confident you wont), then post the gbpvr.db3 file again.
The ability to watch and record now works â rrrraaayyy.
The wash up is; youâre right sub, the first tuner was setup when I didnât have an EPG source, the second when I did.
Actually I found that if there is any difference between the channel mapping of the two tuners - then I have problems with the ability to view and record at the same time.