After further analysis, I have another partial solution, manual focus. The center part of the lens protrudes as it focuses closer. With autofocus it extends and then retracts, jamming the lens regardless. If, on the other hand, one is focusing at a distance at which it does not protrude, one can use manual focus, watching carefully how far the center of the lens sticks out. It won't work very well with closeups, sadly, but with further away subjects, it can be satisfactory. I discovered this while at the same waterfall that started this thread, another sunny day at the coast in January in Oregon.