We discovered one or more bugs in your app when reviewed on iPhone and iPad running iOS 11.0.3 on Wi-Fi connected to an IPv6 network.

Specifically, we encountered an error when tried to login. 

Please see attached screenshots for details.

Do you know if this has anything to do with graph.cool ?

FWIW I think I got such a rejection on an app long time ago (not using Graphcool btw) after doing an update that couldn't have caused such an error, so I assumed it was on the Apple side, just resubmitted same binary and got approved.

I run on IPv6, and connect to Graphcool. That should not be the issue.