Get the Custom Firmware installed on (both?) -T2s and then post some .TS snips of the issue from a recorded file more accurately?
NB You have still not answered which Region / kit is affected. I am also on Sandy Heath like Owen Smith and might do some C4 HD recordings on my -T2 (although we mostly use our Foxsat) if that is the same region as you (BBC East, ITV1 Meridian HD) to see if I can replicate.
Re-encoding using a compressed format (via a phone camera/mic) doesn't help much with diagnosis.
NB You have still not answered which Region / kit is affected. I am also on Sandy Heath like Owen Smith and might do some C4 HD recordings on my -T2 (although we mostly use our Foxsat) if that is the same region as you (BBC East, ITV1 Meridian HD) to see if I can replicate.
Re-encoding using a compressed format (via a phone camera/mic) doesn't help much with diagnosis.