The previous box was a G4 box (500gb one) new one I upgraded is G5 - UHD.
I’m going to see if my other UHD box works in the bedroom without issues.
If the Slx distribution requires power, not going to work as there is no power outlet in the loft.
There is definitely an issue with the tv amp on the DTR T4000. It is extremely sensitive to any issues on the aerial connection.
I buy, refurbish and sell-on Youview boxes. The only model I have trouble tuning is the DTR T4000 and only in my Lounge. I have an amp in the loft and have tried swapping outputs but can only ever tune 7 channels in my Lounge on this model and signal quality is very erratic. Any other box will get the full range of channels and 100% signal. The DTR T4000 tunes normally in my kitchen or bedroom. I think it could be down to a cable problem, this being the oldest and longest, but may also be due to interference from mains cables. Just odd that it does not happen on any other model but always happens on the DTR T4000.