Something has changed on my 5000T. The HDTV option on the change group option changes the epg to display from 101 up as it used to. However if you quit from the epg it no longer selects the last viewed channel but makes 100 Freeview info the selected channel at the top of the epg.
Can’t replicate that on my 5000T either. However, I have deleted channel 100 so not a fair comparison.
I contemplated doing that but wondered if others were afflicted. It threw me a little when I booted the box and it came up on channel 100. I tried playing a recording. I got the audio but no video just a grey screen.