These four images show the disconnector cycle. The partial images shown were extracted from the E-Book, The Luger Mechanicals, by Gerard Henrotin. I highly recommend this informative electronic book for Luger beginners. Just do a Internet Search for Luger E-books and you will find it. It is downloadable and contains many excellent hand drawn illustrations by Mr. Henrotin. The E-book is only about $8.00 and he has written three other E-books on the Luger that are also excellent Luger reference reading...
The first image "A" shows the trigger lever and sear in the cocked position prior to firing.
Image "B" shows the trigger lever has pushed in the sear by applying pressure to the side of the disconnector pin. The firing pin has been released and has fired the pistol.
Image "C" shows the sear & disconnector in between the instant of firing and the point where the pistol becomes re-cocked.
Image "D" shows the pistol in the fired and reloaded position. Notice how the disconnector pin has been compressed by contact with the trigger lever prior to releasing the trigger. This is the point where you claim your slide is one millimeter back from the foward position. The only way this could happen in my opinion is if the disconnector pin does not compress properly upon contact with the trigger lever during the forward movement of the slide. This would hold the action open until the trigger lever is moved back to the pre-fire condition.
You should be able to compress this pin by pressure to the rear of the pistol. If it hangs or is frozen in the extended position, this is your problem.
Once again, my thanks to Mr. Gerard Henrotin (also a member of this forum) for his excellent illustrations...