My driver door handle and lock cylinder are loose. I removed the panel and saw that on e of the two nuts holding the door mechanism fell off. Found it in bottom of door interior. What would make the lock cylinder loose.

 

The cylinder fits snug onto the handle backed up by it's locking rod.

Removing-and-installing-exterior-door-handles

 

The lock cylinder is easy to fix, once you replace the nut there should be a locking C type clamp to hold the nut in place. If the C clamp is missing the nut will eventually come off from the vibration of the door being closed and the lock being used.