That washer appears to be bent on purpose on the linked website for replacement parts and I’m guessing that it would keep the tension on the threaded dowel consistent. I think mine is missing or it was flattened out when someone torqued the mechanism.
Upon further research that is a bowed washer, spring washer, curved washer or wave washer. Their purpose is to retain tension and it’s likely the solution to my gears binding. More can be explained in this video: youtu.be/sG1gSQGZQl8?si=nQhzR2a8TZUwJ5rY