Haven't logged it with NTL... didn't realise it to be that big an issue. I accepted that I was fussy about what order I wanted the channels to be in, so accepted that sometimes I need to tidy it up a bit.
The pace box we had previously never did it though... I may log it with them next time it happens - the event log on the stb may prove useful
edit: now I think about it, we have started getting some kind of "morphing" on the picture, but as far as I can make out, it only seems to be with the terrestrial channels through the NTL box (1, 2, 3, 4 and 5) - I never watch much on those channels anyway

I always thought I'd just raise it with them when I have another problem - get it all over and done with at the same time as its not affecting me much at the moment.