Netlify Proxy: This web property is not accessible via this address

Getting This web property is not accessible via this address.

My Configuration
I own and have full control over the derock.dev domain.

I’m accessing poroscout.derock.dev/mmr/distribution?...
poroscout.derock.dev → (behind Cloudflare) → netlify
on netlify I have a rewrite setup that proxies → porogen.derock.dev
porogen.derock.dev → (behind Cloudflare) → my backend server

Additional Notes
This issue also seems to happen randomly.
My guess is that every reload changes what Netlify cdn node I hit, and some of those nodes have issues with CF.
I think that what’s happening is that some of the Netlify CDN nodes have been “rate-limited” by Cloudflare rays and then it shows the error.

How can I resolve this issue?

I was told to create a support ticket, but I’m on the free plan, so making a community post to see if someone is able to help me here/or can escalate it.