Burst problem

Hi guys,

i got a used ctw m4 mx2 these days and it has a little problem.
The gun shoots in semi mode and in full auto mode only burst.
what part could be damaged?

coult it be the EL002?

It could be that you have the single shot and 3 round ECU unit fitted (GBX-001).

That would be the most likely cause, or if it is sporadic then it will be the same part anyway as the EL-002 is not the control unit, it just tells the gear box when to go and when to stop.

I changed the El002 but now if i shoot, the gears dont go into the right position back. What could be wrong?