King Arms M4 AEG firing problem

[Slodin]

god, i noticed so many KA threads.
although it didn't help me, and I'm new to doing any work on my AEGs

so my problem is that the AEG is firing fine on full auto, but on semi-auto, it skips every other shot.

detailed:
on semi-auto, it would fire one BB, then the next shot is a *click*, so it sounded like the motor moved, but didn't move the gears enough. Then the next shot fires fine, and skips the next one. I tried it for like 20 shots, it was all like that. fire, click, fire, click, fire click.......

I pulled the trigger fully every shot and I was using a 7.4v 20c 1500mah lipo via deans.

However full-auto would fire till it's dry, so motor height shouldn't be the problem.

someone had a similar problem: (but missing some key details about the issue)
Bleak angel in the solutions forum said he fixed it and did a number to his wire..But never explained what happened...So I can't really get help through that. (Pm is not useful when the person is never online ever again...)

So any help would be appreciated!
Thanks in advance.