Ellie is fine 99% if the time, but very occasionally (every couple of months) if she's asleep on someone on the sofa and they move slightly she lets out a very aggressive snarl/snap as described in the article. She then wakes up and looks very confused. It feels like she has no control over it and I wonder if it's when she's in a specific stage of sleep.
Interestingly she has never done this in our bed at night.
We have been training her the "off command" which is rewarded with a treat and that now works well even if she's asleep - she jumps straight off knowing there's a piece of chicken coming her way afterwards!