I've been riding a Specialized Sequoia for about 10 years now without any problems. I overhaul the bottom bracket each year and ever since I did that two weeks ago, the crank won't stay on the bike! First, it was just on the non-drive side. I'd hear a grinding sound, then the crank bolt would come loose. After retightening the bolt for about a week, the drive side lock ring started to loosen with each pedal stroke! I know I've got everything threaded correctly on there, I just can't figure out what is causing the problem. I think the inner bracket shell is ok. there aren't any stripped threaded on either the fixed cup or the other cup. The spindle looks ok too. any ideas?