How far did you break it down? Were you trying to do a trigger job? When I did a trigger job, I couldn't figure out why the trigger would not return. Finally, I realized that everything was in the right place, but I didn't have any tension on the trigger return spring. Winding it around once resolved the issue.
Do you have the .40 upper on a P-11 frame, or was this .40 from purchase?
Feel free to email me directly, if you like. If I don't know the answer, I know several super-knowledgeable types who can probably help...
John