Picture freeze but audio continues

Couple of times over the weekend on live tv the picture has frozen but audio keeps going. Both have been on BBC channels (possibly the same channel we can't remember exactly).

Might be coincidence but on both occasions it seemed to happen when the broadcast was changing format. Once when they went to show a clip from an old TV show and another when they went to "hawkeye" replay on the tennis.

The feed is SATIP. Signal strength is good. Changing channel and back fixes it.

Anyone else had this or any suggestions as what to look at? Running Beta 6.12.1009 on Nvidia Shield TV 2017.