Make shift fix....that’s all. Something to get you by until a better idea comes along. I’m sure someone will have a better idea and a more permanent idea for you.
You might even put the washer in place, then where I have use aluminum foil you could try a good bead of this latex sealant, which is not permanent. That would allow the washer to spin freely against side of stove.
It might sort of bond the washer to shaker grate rod extension and help hold washer in place semi-tight against stove. You will still get some air leakage between washer and stove, but at least most air would be stopped. Sealant can be peeled right off too when you’re ready.
https://www.rutland.com/product/seal-it-right-fle ... aec8db952d