Ok so heres the background. Just rebuilt the motor. Damper was in use on previous engine but in excellent shape, not many miles. Euro damper.
Rotating assembly was all balanced together, damper, flywheel, even pressure plate (which was way off btw, ACT). Multiple people had their hands on it prior/during process.
Final long block assembly by Winters Racing.
I was adjusting mag clearance for crank trigger and grabbed the damper to rotate crank a smidge and felt damper move on crank. It can be rotated slightly by hand and has slight wobble side to side (perpendicular to crank line). Using the same damper, same damper bolt and stepped washer as before. I can pull the bolt and simply slide the damper off by just pulling by hand.
I swapped to a shorter bolt and same symptom. Appears to be bottoming out on oil pump gear, in line with where it should be on the front seal, but just slips off/on. WTF
Has anybody experienced this? My guess is somehow the crank snout somehow undersized or the damper is oversized, praying for the latter.