I broke my original mirror and my junkyard spare mirror because I applied too much pressure trying to get that ball back into the socket on the back of the mirror. I ended up going to Autozone and buying an aftermarket replacement... incredibly frustrating experience... If you swap a mirror, I recommend removing and installing the mirror assembly as one piece.

Though, that spring that is on the mirror mount is quite a PITA to work with as well...

__________________
2006 BMW M5 "Heidi" @ 109,000 miles
2005 MBZ C55 AMG "Lorelai" @ 165,000 miles
1991 MBZ 300E "Benzachino II" @ 165,000 miles
1990 MBZ 500SL "Shoshanna" @ 118,000 miles

(On the hunt for a good used M103 engine as of 6/10/23, PM me if you have one to sell!)