There are a lot of Zeiss 135 mm Sonnar lenses used on the Contarex that have a stiff or locked focus ring. A fair amount of information is found on the web about these lenses suffering from threads that lost their surface finish and were mechanically jammed and all manner of discouraging advice for DIY'ers. I have one of these lenses and it was totally stuck. I am by no means a trained nor experienced tech however I was able to repair it. Here is an explanation of what I did to repair my lens. First I removed the front knurled ring using a rubber stopper purchased at Ace Hardware. Once this ring is removed, you will find multiple screws that hold the optics assembly in the barrel. Remove the optics in one piece. I then used a significant amount of heat to soften the lubricant that after 40 or so years had solidified. To heat it I put the lens barrel (with optics removed) on the upper shelf of my barbecue grill (yes you read that right). I brought it up to around 250 degrees and left the barrel in there for 5 minutes. I used welder's gloves purchased inexpensively from Harbor Freight to handle the barrel once it was hot and give me the grip I needed against the stuck lens barrel. The first time I tried to move it, it did not budge. I put the barrel into the grill for another three minutes. At this point the barrel freed up. Once it cooled down I disassembled the lens mount and separated the barrell and helicoid. You will encounter screws along the way that the Zeiss engineers decided they wanted thread locked. I found that small drops of lacquer thinner on the screws eventually loosened them. All of this was done by meticulously marking the positions of all components so that they could be reinstalled correctly. Once apart I used Ronsonol to clean both halves of the helicoid. I removed all traces of old lubricant from the threads. This is critical because any trace of old lubricant introduces a bind into the mechanism once you reassemble it. Once clean I lubricated the threads (completely) with synthetic grease purchased from Microtools (they call it #10 hobby lube). Once reassembled the focus action was incredibly smooth. I saw no traces of worn or gaulled threads as "web wisdom" had warned about. I hope this information helps. I have no doubt most of the 135mm Sonnars in stuck condition can be fixed this way.