If you notice this only during TNT NBA broadcasts, I will guess the issues are with the broadcast, and not the Tivo.
I think I may have noticed the issue myself. I think I may have even noticed the same issue on NBA TV channel, but I think the same studios and "broadcast chain" are being utilized, by and large.
If it happened on other stations, I might worry. I'm on Comcast cable btw.
Tivo HD Lifetime 1TB int, 1TB ext
Tivo 540040 400 GB Lifetime
Tivo S2DT 750 GB msd
Toshiba sdh400 r.i.p.