Ionic / firebase ipv6 Auth ios app rejection

I have encountered an odd problem the second time submitting an update to the app store.

I am building an app using Ionic Framework with a Java backend. Right now we use Firebase for user login.

We had a tough time getting our app onto the store this June because our server did not support ipv6 originally. After setting this up we got through review. But now that we are trying to submit an update (with a new reviewer) they cannot log into our app over ipv6 from a fresh install.

After further testing, we realized that our firebase url does not appear to be reachable over ipv6 (although we still haven’t replicated the app review’s report - our test correctly displays an error message, but they said that the app freezes).

I find it hard to believe firebase is not ipv6 enabled, but the testing indicates that that is the case. (once logged in ipv6 works fine with our server, we think firebase’s capability to auto-relogin users offline is why we mistakenly made it into the store in the first place). Has anyone experienced similar issues with your firebase app? What did you do to resolve it? Did you end up having to abandon firebase or does the problem lie elsewhere?

p.s. I’ve looked long and hard but couldn’t find any documentation about fireabse’s compatibility with ipv6 or lack thereof. If anyone has seen this kind of documentation, that would also be immensely helpful.