Star L85a2 not working on semi, help please!

[ajn]

Thanks in advance for your help,

Basically, just took my L85 apart to fit a new hop rubber and put it back together and semi is now not working..

It will fire one shot on semi, then will not work again unless switched to full auto or release the spring tension.

I have taken it apart and it seems like whenever the trigger is pulled on semi, the piston fires and cycles another half, leaving the piston in the middle of it's compression.

Just wondering what the hell I can do/try.

Thanks!