Why is the mirror vibrating so bad I can't see behind me?

1. NOBODY seals the OUTSIDE mirror mount screws/bolts. In 37 years as a Tech, I have never seen any sealant to prevent rust to the mount screws.
2. The OP has a 14 year old motorhome. So, yes, after 14 years some things will rust or come loose.
3. To the OP, REMEMBER the wire Chafing problem on F-16's years ago? (Ft worth built). Even Aerospace has quality problems.
4. If this was a BIG problem, you would see mirrors in the ditches, Doug