Tokyo Marui M14 Help

Hey guys, figured I'd make this post and see if I couldn't get some help from the fans who are a little bit more active/savvy in the tech side of things. I shipped my TM M14 off to a fellow member of this boards and now it appears as though he's having some trouble. When he fires the weapon (Or, attempts to rather) all he gets is a click for a response. The weapon doesn't actually fire. Now, I thought at first maybe it's because he had an 8.4v pushing what a 9.6v should be doing as far as the motor is concerned, so I asked him to charge up the 9.6 I sent with it and give that a try. Same results.

So first I tried to see if it wasn't the gearbox that pooped out on me, so I asked him to loosen up the spacing between the gearbox and the motor and see if it still turned, he says it does. Now I asked him to fidget around with the spacing and maybe get that part right, and so far he says he only hears the click now. So in short I'm wondering what could this possibly be?

I asked him to check out the weapon for any missing/stripped teeth/spurs as well as check the piston to see if it would move on its own will when the spring is pushed back with a screwdriver, all with positive results here.

So AirsoftSniper, I ask you what could he possibly do to get this weapon back in the fight? Or what do you think is not right with this situation?