John
I had a similar problem with my viper. Went through 2 of them. Check if it is a really tight fit. In my opinion you don't want it to have pressure from the forward or rear. if it is a tight fit I sanded the viper on the front and rear so it fit in with no pressure. After I did this it has not broken again.
The glass was coming loose at the top of the optic and pivoting rear. Then your dot is way off
When I used a plate in the dove tail, I never had a problem. there was no pressure on front or rear.