Status update on my jammed sander: I went out and looked at it, and
after about 20 seconds of fiddling, it came right off. As Kate and
David have already mentioned, the locking collar needs to move
towards the body of the sander, not away. It’s a little stiff, so
I’m not sure if it’s related or not, but mine came free easily as
soon as I started rolling the drive-wheel by hand, just to get the
shaft moving a little.
Best of luck.