Once I was gliding down a hill and I bumped into a small stone/relief and my character got propelled into the air and died on the fall.
Something similar happened to me chopping down a tree. I guess I was too close to it and when it fell it had a trampoline effect because it rested on another tree and sent me flying a bit in the air. Fortunately this last time I didn't die as I had over 100 health. I tried to repeat it so I could recorded but after several attempts I couldn't do it. I guess they're very rare occurances.