Music programs on Ultra HD ch 228 have chronic stuttering or baulking, it is probably video as well but the audio is obvious. If the channel is live paused for say 30 seconds, then played, the playback is normal.
Help & Support suggest that updating firmware might help but there doesn't appear to be any information about how to do that in the support pages.
The problem did not occur on other HD channels, I never watch sports channels so don't use 529, but I thought 228 (and 999) was the only UHD channel, it is certainly not well publicised if there are more.
I went through the "something wrong with my V6 box" help and it basically said switch the box off and back on, which I did, this was when 228 was off air, but when programs eventually came on, all was back to normal.
The UHD channel is now behaving normally, I guess the power cycle trick is the answer to most issues on any piece of electronic equipment.