Huh. I’ve been riding horses for 25+ years and I have NEVER had that happen.
Much less from a saddle that should be good quality (Crates). I would absolutely be contacting them about the problem.
Can you feel any sharp edges on the Blevins buckle?
Mine always sit lower. Never have had a problem. This isn’t the best picture, but you can see where the leather-covered blevins buckle sits on my grey horse.
http://i84.photobucket.com/albums/k27/r_beau/2014%20Horse%20Pictures/RedandShotgunatMandan_zps974ef828.jpg
Can you take off the fleece cover and show us a picture of the buckle? Maybe there is something “off” with it that we can see.
While I agree you need to put some twist in your stirrups, it won’t make the buckle lose contact with the horse (as you can see in my picture). That saddle is a Circle Y that I bought new over 10 years ago.