Crestline casement window crank replacement
Looks like the worm gear stripped out. This can't be replaced or repaired, unfortunately, which means you will need an all new operator.
I'd be happy to help you ID a match, but I will require a clear photo of the complete operator mechanism. You can review the photos above to get an idea of what we need to see: a bird's eye view, with the link arm(s) in full view. We'll do our best to assist you from there.
If you have the same problem as above, then you will need to pursue the same solution: replacement of the entire operator mechanism. Your next step will have to be to carefully review the dimensions and design of our product above to verify that it matches your original. If it differs in any way, then please remove it from the window and show us a photo of it by itself and without obstruction. We can then try to find you a better option.