[DML]

Joe:

This beginning to sound familier. The failures to feed, (shells not feeding out of the magazine) could be a kinked magazine spring and/or it's getting caught in the space where the magazine extension screws onto the magazine tube. As said before, the best way to check this is to replace the spring with a standard spring and magazine cap. Also, there may be crud or excessive Parkerizing in the magazine tube itself. This could cause the follower to hang up. Try running a tight patch through the magazine tube and see how it feels.

The failure to unlock could be the action locking arm (bar?) on the trigger group. I have seen a few of these hang up because of burrs on the bar itself on the left side. I am looking at one right now that has really bad burrs as it came from the factory. When the hammer falls it is supposed to release the lock, but it doesn't always work that way if things are rough. You might try to lightly
polish the end of the arm just enough to remove any burrs. With the trigger group out of the receiver, pull the trigger while holding the hammer and release it slowly. You'll see how it works.

One last idea. There is a good chance that none of the parts in your gun are the ones that were in it originally. Take a close look at the camming surfaces on the action bars assy. and the end of the left side in particular. Look for excess wear and dings.

That's the best I can do without actually seeing the gun.