Hello there, I need some help about a problem that I'm having with my M904, I recently have taken it apart, and after checking the shims and greasing the gearbox, I have put every together, and while checking my fire selector it's not working, I don't have a semi mode anymore, every time that I shoot it just does a burst of 2 shoots, and it does do same sound when you connect the battery, everytime that I press the trigger!