I've got a young spider ball that just started doing the same thing. 2 meals ago I switched from adult mice to weaned rats. My spider would always strike and constrict a mouse live or frozen for several minutes before eating. If he didn't want to eat I would try the "leave in for a while" method and the snake would never eat it. It had to be struck and constricted. Now that I'm feeding rats he hasn't struck at all, but I lay the rat in the cage and it's gone in a few minutes. So strange to make a change like that instantly when it came to new food.