Is it the whole mirror arm that is folding or just the mirror part?
I have a 2023 Plus Four so the older trad style mirrors. I replaced the original mirrors with Librands round ones as I preferred them for visibility. I seem to remember that there was a screw that tightened the mirror up so it stayed in position. I can check later. I can remember making O-rings to help seal and cushion the mirror, but that might have been on the previous car. This was at the ball/socket joint on the rear of the mirror. The grub screws holding the stem in the base were checked for tightness too but be careful there! The base arm is not hard material so care not to damage the thread is needed.
