Edge Function returns 500 errors: Invalid URL: '/.netlify/internal/ef-cache'

I’ve used Netlify Edge Function as CORS Proxy.

However, Edge Function returns following 500 error since 2023-08-25.

Invalid URL: '/.netlify/internal/ef-cachehttps://www.inoreader.com/oauth2/token'

From the error message I can infer that there appears to be some kind of internal error.
I checked the “Edge Function log” in the admin panel, but nothing was logged.

Similar: /.netlify/internal/ef-cache/? - Support / Edge Functions - Netlify Support Forums