As reported in the thread Permanent HD Display - #17 by angus.black which is on the same issue, the problem seems to be something to do with changing the resolution of the cam pan. In my case it was resolved by changing the resolution from 360, which it had gone to spontaneously, back to SD.
I got a very rapid response to the ticket I submitted. They were going to suggest experimenting with resolution, but our Forum, in their words, beat them to the punch 