If you're handy, there's a neat little fix that will help.
The right mirror sticks out front in what is called "clean air" ,very smooth and stable as the mirror moves forward.
The driver mirror is surrounded by "dirty air", that has hit the windshield, changes direction, then goes around the side of the coach, another change and hits the mirror causing a significant vibration at times.
I cut a small stick to go between the window frame and the top of the mirror head. The stick is held in place with Velcro on each end and is about 1/4" longer than the space. That way the stick wedges tightly between the two, and tends to stabilize the top of mirror head from movement. The end that goes against the mirror needs to be form trimmed to fit the mirror to stay in place. Have done this on two coaches with great success. A good coat of hammered spray paint makes it look like it's possibly right from the factory, or at least aftermarket, not just homemade.