Do you have any locked down policy on them though? I assume this would only work if you gave blanket access.

I noticed in my tests it found one on port 3000 with blanket access, but didn't see one on port 9999 with restricted access( policy => allow from *.mydomains )

Yes. I'm terrible and have them set to allow all domains, and all methods.

Maybe your browsers are up-to-date?