[1tonne]

This is a common problem with some of AA's older triggers (So you may have bought it recently but it has most likely been in the shop for some time). Like Oddsyns said the spring guide stopper is a little too wide.
You can either file the sides of the spring guide stopper (and maybe the trigger sear if it ends up getting stuck too) or you can file the edges of the cylinder where the spring guide stopper fits into. You only need to file it a very small amount so check it regularly when filing it. You want the spring guide stopper to fit snug in the cylinder slot but not to grip on at all.
With mine I chose to file the cylinder slot a little so that the trigger would still have it's full strength. Also, the Teflon will not flake like some people suggest.