--edit--
Just reread the doco on this and page 54 says"
I was selecting cancel (and stop) from the timer viewer rather than the video view - is this the problem? Am I meant to go from the timer view to the video view and end (cancel) the session from there? If so, (to me at least) it would make more sense that canceling it from the timer view should be all that you need to do.So let’s finish the session – we have returned to the pits and we stop the final, incomplete lap pressing the Cancel button in
LapTimer’s Video View. Again, this will stop video recording on the master, and for both satellites. In addition, it will void the
last incomplete lap like usual.