I have never found this to be the case with ball pythons. You should always feed on tongs and make sure your hands do not smell like rat. Also make sure the rat is warmer than your hand. You need to follow the same procedures every time you feed or handle and make sure those procedures are different. If you do this the animal is far less likely to become confused. There are times that feeding outside the enclosure becomes productive, but they do not apply to your situation.