Yes, I first noticed the problem when I used the numeric pad to change to Sky News on channel 132, as this is much quicker than using the programme guide.
Both Sky News and the programme that I was watching are within the same group.
I followed your instructions exactly as to ‘sticky keys’ and the result was the same.
The programme up/down buttons will change the TV channels within the Favourites Group, but as soon as a TV channel is selected using the numeric pad the “favourites” are replaced by the defaults.