Hi!
I had somewhat similar problems in the beginning with my Aztek. Moisture trap helped a bit. The main reason for leakage was loosely tightened nozzle, I had to use the tool that came with the AB, just couldn't get it tight enough with my bare fingers for some reason. Maybe I was affraid to break the damn thing...
But if nothing seem to help try to dump those gravity feed cups. Use the ones that need air pressure to suck the paint out of the cup (whatever it's called).