A lot of ship can happen when you're not warmed-up.
I was doing drills in BJJ, back in the late 90s.
Just from the guard, right hand up into the collar, left hand encircling my opponent's right arm, coming up the opposing collar.
Just a simple drill. Not even fighting, not even rolling – opponent was just still.
We drilled the same circular, overhand encircling of the opponents right arm, from the guard, 10x each.
In the middle of doing this simple exercise (again, non-combative, just drilling) ... I felt "a trickle of water" in my left shoulder ... didn't think too much of it though.
The next day, I couldn't even put my left hand behind my head.
I couldn't lift my left elbow even level with my shoulder.
For 6 months, my left rotator cuff blown.
Crazy stuff can happen, even at a soft level.
Honestly, that's especially as men get older. I was in my early 30s at the time.