H&K 417 stuck in semi. HELP

[Steve8182]

Bought a 417 yesterday and worked fine. Charged the battery today, after being sent the wrong battery, and couldn't get it to fire in full auto. I've tightened the Allan key that holds the switch in place after being advised too, then it stuck in safety. Soooo, I loosened the Allan key a tiny bit which released into semi, but there's a little wobble on the switch now. If I wriggle it and turn into full auto it works. But then switches straight back into semi,

Any ideas any1?

 

[Mike636]

Did you buy it from a shop?

 

[Steve8182]

No mate, second hand. You could call it new though. Not a single mark on it. Just been a wall hanger. I've just been playing with it now. If I push the selector and turn it it will go through all the modes and stay in those modes. But if I push as normal it stays in semi