I have seen a number of people claim that they were squeezing their shoulder blades hard and still not have back tension. The muscle group between the shoulder blades do not automatically guarantee anything if the rear shoulder muscles are not in the game. If the arrow and the arm are lined up, when the draw gets far enough back all of the muscle groups come into play, some say that it can be seen in chest expansion. When I have seen people having a release that either pops out or does a wanky offline jerk, it is usually tensions that not in line with the arrow. It is proper that the release hand would want to skid back a bit, that is a product of reserve back tension at the release. If it pops out away quite often either the wrist was not straight, the hand was cupped or the arm and shoulder muscles that move the hand that direction were in play. My son use to have a pop out pluck when he was 14. He shot pretty good with a Hill Big 5, but when he tried to shoot a two wheeler, he produced the wacky arrow wag that i have ever seen. I held my hand up a good foot from the side of his head. Bang, he hit my hand and then yelled, "Why'd you hit my hand, that hurt." He would not believe me, until I showed him a video via my neighbors camera. He had it all, the cupped hand, bent wrist, torquing of the bow string fingers, elbow not coming back until it lined up with the string. Once that was understood and straightened out, he quickly became one of the best shots that folks around here have ever seen. I could still beat him on moving targets, but he had me on the anything standing still. To this day 20 years later, if he cannot shoot 6" groups at 30 yards, he thinks he is having either an arrow problem or he is having form problems.