There’s some wierdness with FF on Big Sur and rendering

Hi - I noticed this on Aurora, switched to beta and it’s still failing.
There’s some wierdness with FF on Big Sur (just updated to the latest minor point release) and rendering. It’s like certain CSS is not working. Log messages seem to point to CORS, but this isn’t consistent. I have a site running tt-rss (which uses dojo) and this display regression just started after the Big Sur update. I know the tt-rss javascript hasn’t changed. However, tt-rss isn’t throwing CORS errors.
Failed to load ‘’. A ServiceWorker passed an opaque Response to FetchEvent.respondWith() while handling a ‘cors’ FetchEvent. Opaque Response objects are only valid when the RequestMode is ‘no-cors’.
I’m not sure what else to do now. This post is coming to you in Safari.

¡Hola @jchimene!

Can you please share the URL of the page where you observe the “weirdness”?