I'm not super familiar with 1940s Voigtlanders, but it's a folding camera, correct?
I'm not totally sure what the owner means...if it's just that the rangefinder doesn't couple to the lens at closer ranges, that may be normal—every lens can only focus so close, and a coupled rangefinder wouldn't allow you to focus any closer than that. For example, I have a more modern Voigtlander Bessa and the lens can only achieve focus at around 3 ft, so the rangefinder accordingly only couples properly to that range, and anything closer will not focus. It's not a flaw with the coupling, it's just telling me what the lens can do.
However, if the owner is saying the coupling goes out of whack even within the lens's focusing range, that would not be normal—unless this is some peculiarity with this particular camera, but I doubt that.
As long as the camera and lens are working, you should still be able to focus even if the coupling mechanism is wonky. You would just have to estimate the distance form the subject and match it up with the distance indicator on the lens.