Wobbly mirror

Hi all, my left hand mirror starts folding back at speeds over 60mph - standard oval mirror. does anyone have a simple cure for this as apart from that they are fine. I have tightened up the bottom bolt but it is the top ball joint that moves.Cheers mook.

You can buy a new crush sleve.
On my 07 I took a 45 auto shell and cut off the base then split it and then kept tighting till it was tight.
It has been good for 14 years.