Have you practiced with your broadheads? Do they hit the same as your field tips? If your grouping 2' out at 20 yards its probably not a bending at the waist problem. Unless your about 50 feet up in a tree. Theres just not a lot of bending involved out at 20 yards. Try a good arm guard. Practice shooting in the clothes you hunt in. And make sure your bow is tuned to shoot broadheads and field tips the same. Your not by chance shooting a Trophy Ridge flatliner type site? They've been known to work loose now and then.