'Lil MP5 problem

[TacMaster]

Hi all.

I've never really had problems with my MP5, however recently after opening the gearbox, deep cleaning it and re-installing it I've noticed a small issue:

On semi automatic, when I pull the trigger it stays back instead of springing forward; however this doesn't happen on fully automatic.

Is this just a trigger spring problem or is it something more serious?

 

[AK47frizzle]

Your cut off lever and tappet plate may be interfering in semi as you may have done something wrong when putting the gearbox back.