Apple TV 4K - a bought iTunes movie repeats for a few frames then audio is out of sync

I've bought "The Fifth Element" from the Apple TV store.

At 1hr, 19 mins and 38 secs the video skips back a few frames which puts the audio out of sync.

This doesn't happen on my Mac mini through the Apple TV App, only on the Apple TV 4K.

Also this is the only time it has happened with any film.

I'm guessing there is part of the film that has downloaded badly and is now in cache?

Is there a way to delete the cache or do I have to reset back to factory settings to get rid of this?

I tried email support but just got stock answers. At one point they refunded the film without me asking them to! I didn't want a refund.

Any help would be appreciated.