Originally Posted by
ianjk
Probably time for a new crank arm. Guessing that the inside surface is all marred from "wobbling". It just takes a couple "wobbles" for the surface to get messed up, no matter how hard you tighten it, it will move a little when you pedal, slowly unscrewing the crank bolt.
+1
You might have rounded the cranks from all that accidental untightening. Also, I believe tightening the cranks involve a torque wrench (it has to be super super tight)