It's always good to test them out if possible before buying. As for Bulkhead and Megatron, they don't appear to need as much pushing of their chest allegience symbol - so if the head doesn't move even a little bit, I think it is faulty. And I don't think there is any allignment issue either, because the head and chest sections don't move in the transformation (both have their heads covered in vehicle mode). As such, I wouldn't risk buying one in the hope that you could fix its mechanism.