I am aware that this issue has been raised over on the EE Community under a separate thread for watching ITVX. However my O/H was watching one her recordings of George Clarke’s Amazing Spaces yesterday when she encountered the same problem. I was watching the cricket in the back of the house and couldn’t remember what had been discussed on the other thread. The recording is on Channel 4 HD and the box is set up in aerial mode. She has 11 episodes of the series recorded which appears to be significant according to comments in the other thread.
It's being investigated, but faults like this are rarely fixed quickly.