Workers on Custom Domain receiving 522 error

I have a Worker which can be seen working at https://favicon.potherca.workers.dev/ however, when I visit it at https://favicon.pother.ca/ I get Connection timed out Error code 522

I don’t see anything wrong with the settings.

I noticed that some other workers are also getting a 522 (https://curse.pother.ca/ and https://cloudinary.pother.ca/) but not all (https://gist.pother.ca/ works fine…)

Can anybody give me an idea of what could be going on or where to start looking for fixes?