Help with WE smg-8

[p wheels]

I need a little as I'm new to GBB guns. I've got a problem with my WE smg-8 where for some reason it won't cycle properly. When it's fired on semi it starts to fire ok for a couple of shots then the BB's just drop out the end of the barrel & then the gas from the disperses all at once, full auto does the same thing.
I took it apart & found that the loading nozzle When pulled back doesn't slide smoothly & if I cover the gas part & end with my fingers it moves back & forth with no pressure. Is this right??
Also found a npas valve in it but it can't be adjusted as it hits 2 prong things at the back. I took it out & replaced it with the standard valve but it does the same thing.
(All test shots have been fire at room temp)

Please can someone advise me as it's doing my head in!

[p wheels]

Re: Help with WE smg-8

Amazing, posted the same question on another forum at the same time & had 8 replays which has helped me out & yet on here nothing.......

Disappointing.