[mrerick]

It's possible that a part in the overall trigger linkage is not in the correct position, or that it as been modified to the point that it no longer is large enough to work.

First, I would take off the trigger plate and see what resistance you encounter operating the sear bar by hand (pushing it in in front to rotate and release the sear. If it's smooth and crisp, the sear to firing pin linkage is probably ok. Observe how much movement is required to release the sear.

Look at the surfaces and see if anyone has modified them, grinding them down.

Next, I would make sure that the trigger plate fits solidly against the side of the receiver. Make sure that there is no play when the locking lug is in position. Check this by operating the trigger and watching to see if the plate moves in and out. If it is loose, the plate or locking lug was probably damaged in some way.

Finally look at the trigger bar in the trigger plate. Look at the surfaces to see if they have been reduced to the point of becoming too small to press the sear bar properly. Compare the transfer bar to the ones in your other Lugers...

This may help you find what parts are contributing to the problem.