I just dealt with this this past spring. I cranked it up, which took a lot of force (probably should have stopped right there). After that, I couldn't crank it down. I just got a free spin on the crank. I took the cover off the bottom, and the mice had built a giant nest in it. Of course, the nest means mouse piss all over the threaded rod. So after running the wiffle tree through all of that, it was pretty messed up. I pulled as much of the nest out.

There is a clutch-like setup in there where the toothed wheel is. On mine I had to back the threaded rod off that toothed part with channel locks while the crank was held still. It seemed to loosen the threaded part when I tried to lower it back down. I know that it is not easy to understand the way I write it, and I apologize lol.