The focus action on the lens should not be so stiff as to cause it to unscrew. If it is that stuff, a Lube job is probably required. I use this lens on my M8 with an LTM to M-Mount adapter. I "cheated" and worked a little sewing machine oil into mine. When received, it was very stiff.
The lens was left alone for several years, I think, so a "lube job" might be appropriate here, too. I have never lubricated a lens, could you give me an idea of how to do so? And, is sewing machine oil like shredder oil or like 3-in-1 oil?
Sering machine oil is light, maybe a little more refined than shredder oil. Look in the back of the focus mount, with the camera at closest focus. Seems to me a couple of drops of oil into the mechanism at that point could be worked in while moving from 3ft to infinity.
I checked mine- and that is how I worked the oil in. Set the lens to min focus, look at the rear. There is a cut-out section that exposed the back of the helical. Drop some oil a little at a time and then work the mechanism.
I will get some oil and try it out. The mechanism seems to be loosening a bit anyway, but that would help. I think I need to experiment with some other adapted lenses, because I like the manual focus and quality of this one, especially for stationary objects (relatively, these blow in the breeze a lot).