device stops recording

I have a new Edge 540 with no sensors attached. I'm able to download a course and begin navigating the course, recording the ride as I go, but part way through the ride the recording will just stop, as if I've told the device to stop the ride. But I have not stopped the ride. Yesterday it stopped recording 22 miles into a 71 mile ride. This was a PIT stop where we did stop riding for a while. Did the ride time out? If so, how can I prevent this or work around it?