Hello, I am hoping somebody can weigh in on the following issue: I recently purchased a Zeiss Super Ikonta B, which appears to be in good working order. Yesterday I noticed that the focusing ring seems to be stuck - I can turn it freely (using the little wheel or else directly turning the ring) between 1.5 and 1.8m, but there is a hard stop at 1.8m and it cannot be focused to 2m and beyond. The focusing ring was definitely turning all the way to infinity when I bought the camera, but something happened in the intervening few days. Any thoughts on how to fix the jam? Thanks!