Based on it just being BT Sport, could mean there is an issue with that channel in particular, however I would advise you check all connections are tight on the back of TiVo box and also at the wall and any connections in between
If I've helped let me know 🙂
10 year's managing 9 Virgin Media accounts, and things never got any better, closed last 4 accounts since January 2021 :L
I give 'my' experience to help where possible.