RE: big carp problems
Almost every pull-off I've experienced was because of lack of penetration where the point doesn't exit the fish, or hitting near the tail or too low in the gut where the flesh tears too easily to survive a sustained fight.
What points are you using? Some points allow the fish to spin-off.
If the barbs on your points are on the part of the head than spin when you reverse the barbs to release a fish, you could be getting spin-offs, but I usually see that on smaller fish that thrash like wild. If the point is loose when you reel it in, then it may have been a spin-off.