hmm its late now here, so I am not gonna shoot now, but first think tomorow.
but I have found this:
http://gasguns.info/forum/viewtopic.php?t=3105
person had same problem:
When set in semi mode, the gun is able to fire one shot then the trigger gets stuck. In order to fire the next shot, I'll have to push the trigger forward and hear a "click" sound. This problem reoccurs after each round fired in semi mode, but does not occur in full auto mode.
but I also seem to have the problem in auto mode...
So tomorow I will adjust those springs and see if if helps.