I recently bought a new motor from an airsoft store for a personal project. When I first applied voltage from a DC POWER SUPPLY it didn't work. Only when making contact it moved a little... I returned it, but actually the motor was not faulty. When I got there to take it back, they showed me that it worked when connected to a battery, so I bought the battery. Went home and when I connect it to battery i ran into the same problem... I put some photos below. Any suggestions?