Every unintended discharge I've ever had has involved a finger on the trigger when it shouldn't have been. Of course, a stick or vine can pull a trigger as well, but I've never seen a safety failure.

Upon reflection, I did used to have an old model 37 that sometimes fired the 3rd shell unexpectedly when a bunch of ducks stormed my decoys. I still don't know whether those were 'slam-fires' or unintended trigger pulls...Geo