Looks like a service centre visit. The camera has always had excessive power drain when turned off (typically 6% per day) so I suspect all has never been quite right. It started giving Err 06 (cannot perform sensor clean tasks) on startup about a week ago. This was after I managed to drain both batteries in the grip by leaving the camera unused for too long. This afternoon, at Chester races, it completely locked up, with just the battery icon flashing empty, no other error code or symbol on the top plate. Turn on and off and it works again - batteries 93% and 95% in the grip - fine for a while, then locks up without warning. AF tracking working, looks fine through the viewfinder just nothing happens when go to full pressure on the shutter release. First time I though perhaps it was because I had it on A1-focus rather than A1 servo and it hadn't picked first focus on the horse, but then it happened a second and a third time. Able to take pictures between times, absolutely nothing obviously wrong. So two out of three races no pics.