paint leak

First thought is that the paint is too thin...have you changed your ratios at all?

Mine did something similar, all I had to do was give it air and it would spray, without me having to pull the trigger back.

I took the nozzle apart, cleaned it real good, then put it back together, making sure I tightened it down really well. I'm not sure if it was the cleaning (it was dirty) or if it was the nozzle being tightened, but it has fixed the problem. I did have to get one of those little red tools that comes with it, I had lost mine. That may have played a factor, too: without that tool, I wasn't able to get the nozzle tight enough.

I guess it could be inside the brush body. I have had the needle (the part inside, not the one in the nozzle) stick before. That can cause the paint to flow when you don't want it to.

I have taken apart an Aztek before. It is easy to take it apart, but it is a pain to get everything back in the right place again. I would recommend taking it apart only as a last resort; see if you can get some solvent in there to loosen the needle a bit.
HTH