I was vacuuming this morning, soon after new carpets fitted. Just before completion, darned Dyson lost power. I thought it was down to my treading on cable and breaking a connection, as I've done once before. So that meant lugging to shed, stripping out the switch, etc. When I could find no obvious breaks, a possible alternative cause occurred to me: the cylinder was chock full and some sort of automatic cut-out had been triggered. Sure enough, after emptying, all was OK!
I'd been holding out until I'd finished, and had planned to take a photo. ("Can you believe all this came from a new carpet?")
There's a label on the machine itself, which includes mention of an over-heating cut-out. I guess that was it?