New hardware needed, teeth on crank(s) are worn

I'm not sure what you have from these pictures. I think you have either our 39-253RB or 39-439B, depending on what it has at the end of the arm. That's not visible in your photos.

Either way, the cover and handle are sold separately; see our 39-452.

These photos don't tell me anything new, but from what you've described it sounds like your operator gears are stripped and not working properly. If you don't think that's it, I'll need you to experiment with the window and narrow it down for me. I don't know what else it could be.

Yep, your gears are stripped. You will need one of the two operators I recommended before. Like I mentioned, the only difference between them is the slider at the end of the arm, which is a surprisingly important detail. You will need to see what style your operator uses to decide which one is the better fit.