Maybe you should inquire in the bicycle mechanics forum. All my bikes have square taper cranks, except my new road bike has Dura Ace cranks with external bearings and a splined interface, except they use a different attachment method with a pinch bolt on the nondrive side, so I don't know what your problem might be. I do know that the bolts on square taper cranks have to be tightened a lot, about 33 ft-lbs, but I don't know what it should be in your case.