I have the same hardware on my windows (just bought a new home), except that the previous owner has removed all of the handles from the cranks. I was able to replace all of the handles except for the ones on the cranks which were missing the actual piece that the crank handle attaches to. The piece that is cylindrical, with grooves in the edges for the handle to "grip"? Is it possible to replace this one piece of the mechanism, or will I have to remove all of the hardware and start from scratch on these particular windows?
It appears you have a damaged gear.
We recommend you remove the entire operator system and replace it.
When you have it removed, take a few photos of it and upload them so we can help you identify the correct replacement.