Can you try going to the Settings->Misc screen, untick 'update epg during live tv', then go to Settings->Channels and do 'empty epg' followed by 'update epg', then check if you have any duplicates?
Maybe the best way for me to tell you why, taking much of the guess work out of it for me, is for you to zip and attach your npvr.db3, and I'll look at it here.
From a digital tuner, it'll record all the streams associated with the channel. ie, video stream, one or more audio streams, teletext subtitles stream, dvb subtitles stream etc.