I will get straight to the point:
My AB's trigger sticks. actually, it is more of the spring thingy on the back of the trigger that sticks. I have the recent Badger version 150 model with the new T slot behind the trigger to put in the little piece of metal.
sorry, I don't have the manual with me and thus cannot give you a technical name for the "spring thingy"

Is this the 150 you have?

Which part are you talking of?? 50-042??

yep
I think it is called the back lever or something

My guess would be then the assembly just behind it is needing a cleaning.

The metal piece in and of itself is not connected to anything, it is just a lever controling the paint flow. As you can see, in the picture, the assembly is screwed together. It should be rather tight, so you will need to control the force you apply so you don't slip and break something else. Carefully take it apart, noting how everything is put together, and clean each individual piece.

My guess is some paint build-up has caused the assembly to stick. You might need to soak the assembly in a stronger solvent like lacquer thinner to loosen up the build-up. The more thurough you are will pay off later on.

Hope this helps, if not let me know. I have had a 150 before and I recognize the pieces from the picture. There really isn't too much that can go wrong on an airbrush, so I'm sure we can work this out together.

Cheers,