I'm just thinking outloud hear.
I've seen people that open the vanity mirror, do their business, then just flip up the entire visor, rathern than first closing the mirror, THEN flipping up the visor.
I can see that if there is a contour to the headliner, or the mirror cover catches on something, this method could stress the hinge, resulting in failure.
Just a thought.
Actually it is a piss poor design. The plastic used is the issue. It is very brittle. Even the cover that goes over the lighted mirrors won't stay closed. Problem with this is that if they open enough the lights will stay on. I figure I can remedy this with a very small, well-trimmed piece of velcro. Just wonder if I can find some in a tan color.
Really sucks having these little stupid troubles on a truck that only has 50K on it. I have this issue, the beloved "Butt Crack" issue on the back panel, and just a couple months ago both front and rear actuator doors started doing the famous clicking noise. At least those aren't expensive fixes just a pain in the butt to get to!!! Dang just about done paying her off and the stupid stuff starts!!!

Up until a year ago when the "Butt Crack" started to show itself, I have had only one issue with this truck which was in it's first year. They replaced the rear differential(3.73 limited slip). It was getting a shudder when turning. From the looks of things that seem to be the norm, I've been extremely lucky!
04 XLT Sport 4X2 4.6V8
Dark Blue Pearl/Platinum
Med. Parchment Lthr Sport Buckets with 3rd row
Class 4 Tow PKG/3.73 LS Axle
Rear A/C, Roof Rails,Reverse Sens.
17" Sport Aluminum Wheels(with silver centr caps from an Edge)