Casement window crank missing retainer clip for spindle (worm gear)

I have a casement window crank that works well cranking the window out (counter-clockwise). But when I try to close the window, turning it clockwise, it just turns freely and the spindle (worm gear) just screws right out of the casing. I believe it is missing a retainer clip that should keep it tight in the casing, based on looking at other windows that work fine.

I'm including 3 photos, 2 showing the missing retaining clip (with and without the spindle) and 1 showing a working window with the retaining clip. The spindle is 2 1/32" in length -- It just needs something to hold it in place.

The opening that the spindle screws into, without the retaining clip, is 15/32".

Thanks very much.

Thanks for your response. Greatly appreciated. But I'm not sure I understand how the gears have stripped if it works fine to crank out, just not in. And if it was stripped, wouldn't I be able just to pull it straight out, instead of needing to unscrew it out? I'm attaching a photo of the worm gear.

I read about two different guys who just pounded the top area, the place missing the retainer clip, with a hammer in order to dent it up so that it would not allow the worm gear to come out. And that fixed their problem, at least temporarily. But I'm not sure I want to damage mine.

But you know much more about this than I do. If you still think it needs a new operator, I will upload a couple photos of the operator. Thanks!

Here are three photos of the crank operator. There's another smaller arm that I didn't take off -- I wasn't sure if you needed to see that or not. Please let me know if you need anything more to make a recommendation.

Thanks.