Mirror cap struggling to clip in

I installed these about a month ago and the driver side keeps popping out like this and I'm afraid it's going to fly off on the freeway.

I can't get it to sit right for more than a few days. has anyone else had a similar program & solution?

 

Angle the actual mirror down towards the ground. Then use a flashlight if needed to look inside and see what clip is not cooperating. You may need a regular screwdriver to manipulate the clip. Hope this helps.

 

Brilliant! Thank you