S&W M41 Trigger Problems X 2

Strangest thing.  Two A prefix guns started doing this at the same time. One of the guns I bought used in 1984. One belongs to a buddy.  One has been to KC for the magazine disconnector disable the other has not.  The hammer on both guns randomly catches on half cock.  I've got a thought in my head that maybe just a good deep cleaning of the frame might cure the problem.  You guys seen this?

I didn't know they had a half cock. How would you be able to see it? Is this an April 1st question?

Had this problem recently on a customer’s 41. The disconnector was set so it barely allowed the trigger to work. Occasionally it would trip as the trigger was pulled and cause the hammer to catch on the half cock notch. The problem on this pistol was due to a new bolt face being proud of the bolt body and not letting the slide close enough to totally clear the disconnector. A little judicious honing on the bolt face fixed it, making sure it still had sufficient headspace to prevent slam fires. 
On your pistol, look at this area in addition to thorough cleaning of the bolt face, barrel face and disconnector notch.

Check the overtravel screw as well.  Rare for them to move on their own, but can prevent the trigger from moving the trigger bar far enough forward to allow the sear to fully clear the hammer.

For you guys that might wonder... You can't see it with the gun assembled.   The hammer falling makes a obviously different sound when it catches on half cock.  
Here is the gun with the slide off and the hammer in cocked position, fired position, and half cock position.  
Cocked position

Fired position

Half cock position

It is easy to tell if the hammer has fallen to half cock. If the hammer is all the way down, the slide is hard to retract from the start. When on half cock, the slide has about 1/4” of easy movement before it hits the hammer and is harder.

Update...  Pulled grips, barrel and slide off the receiver of gun #1.  Put the receiver in the ultrasonic cleaner for an hour.  Looked it over good when putting together and saw the trigger spring off the perch.  Placed it in the proper position, flushed out all the moisture from the frame, and put the gun back together.  Since that time the gun has run 100%....  Next I'll do the same for gun #2...

Issue returned...  Had a plain jane gunsmith look at it.  He recommended changing out the trigger bar and trigger bar spring.  Changed the spring last week, the bar requires a little fitting so it waits, and the gun hasn't missed a beat since.  FWIW the gun is a '62 model.  I'm certain it had the original spring in it...