I have a 11 year old appaloosa mare. Owned her since she was 4 years old. She has many ornery issues and have taken my time to gentle her down. She sways when asleep and sometimes the front legs bend and down she goes on the front side while the back end is still up in the air. I saw her once fall completely down and stay there for a few minutes. Only been ridden maybe 5 times while I've had her. I'd appreciate any comments.
This is a problem that you need to consult a veterinarian about. It could be a neurological problem.......but until you find out what is going on you should not ride her.
Please let me know what you find out, but this is not normal behavior.