I have the same problem!!! I can crank the ***** out of that bolt on the non drive side, until I am afraid of cracking something, and after a few days, it develops some play in it, and I can wiggle it just a tiny bit. it is really disconcerting... I think I need either a new left side crank arm because the hole is not perfectly square anymore, or the BB spindle threading on that side is mussed up.