I have detected the error.

If you notice I return you a processing_url with 202 header, in the spec of NIP96 it indicates that it should not return you neither size nor dimensions nor x at this moment, I suppose that in some update I broke it.

Whenever it returns processing_url you should process it as delayed processing (even though it doesn't take even 1 second).

I have already removed the size and dim tags from the initial response to avoid confusion.

Can you try now?