My Demolishor has a bit of a problem with the treads. At first, the treads would lock into place when I wanted him to go back into Excavator mode. Now, when I try to click them into place, they don't stay. They pop back into an oval formation (not completely the round wheel), but are still loose and don't look right. They click into wheel mode fine, but don't go back to tight treads. Does anyone else have this problem, and does anyone know how to fix it?