The answer is the circuit board on the oem battery you're buying. Besides facing error 29 you will also notice the battery percentage on your iphone is not reading correctly. Use the original circuit board on the new battery you bought and everything will go fine. The problem is you will have a hard time taking out the circuit board from the original battery cos its tag weld to it. The method is to apply heat to the contacts and the battery will slide off from the circuit board.