Recently we've suffered an outage pretty similar to the one described in IPv6 Support on Android from Reddit. We've been using OkHttp 4.10 during the outage. We made a discovery that IPv6 route was broken on the most popular ISP of our user base and for some reason, the app was choosing IPv6 over IPv4 even though IPv6 route was broken. So, we were wondering: OkHttp caches the DNS lookup that was once successful and tries to use it again in future requests? Or is this an OS thing? We are looking forward to update to OkHttp 5 to get access to Happy Eyeballs, but we're not sure if that would help our scenario.

You should upgrade to OkHttp 5