This is one of the reasons I cancelled TNT Sport when my contract was up for renewal. For the last couple of years on and off there have been what I call micro-stutters of the audio on the Ultra channel.
For months it was a known issue in the Nottinghamshire areas and they sorted it out briefly but it never completely went. All the usual posts about changing cables and settings never work, it's an issue for some people with the channel and nobody seems to want to sort it, so they aren't getting any more money out of me for it. It was happening for me (and my local relatives) on both my V6 boxes and one 2 different televisions, neither of which were using external speakers.
Before TNT took over the BT Sports channels, the normal HD channel picture quality was excellent quality and much better than Sky Sports HD for football, but then the quality dropped to the same standard as Sky Sport HD. When it was BT Sport I would often watch on HD rather than UHD because the picture quality was great and there was no glitching on the sound.