Mines a... bit awkward but repeatable. It shows there's something "off" somewhere in the code dealing with fall damage/collision detection.
So... to get this, I mined myself a hellavator.
Went back up, dropped down the hellavator with smart cursor turned on dropping wooden platforms below me and holding down (I'd had a freefall accident without water to save me, figured would clean up the platforms later to have it function normally again).
I later headed down with smart cursor on (to clean up the platforms) and was mining below me as I went down, it missed a couple of platforms which was odd but... no worries.
Falling down it again, it was 50/50 whether a certain platform it missed would make contact and cause a death or allow me to pass through it without issue.
It was a wooden platform that ended up looking like steps going up and left against the right wall of the hellavtor.
Had a few cases where another certain jump would either cause me zero, 5, 28 or instant death damage. Same jump, same height. I'll try and get something exact and replicable.