I've experienced the opposite issue when I got the bike.
Those nuts are so tight that on one side I decided that who ever tightened them had longer spanners than me and when a 18" shifter won't break it apart, it's time to stop.
The mirror glass gimbal joints are also so hard to move too.
I 've found twisting them counter clockwise first, then in or out to get the glass to look up or down is the only way or I feel the mirror glass will break with the twisting force.
I can bump into the mirror with a arm or elbow, and nothing moves.