IPv6 Issues Android

This is going to be the worst bug report, but I've had issues with UnityWebRequest and IPv6 endpoints.
This is using 2018.4.14 and above.
On app startup sometimes web requests will refuse to connect to any IPv6 endpoints, its intermittent and I have no way of replicating it yet so I am just wondering if anyone else has had issues with Android and IPv6.
Tested on WiFi, 3G and 4G, stable connections.

The only way I've been able to prove IPv6 is the issue is by removing the AAAA record for the endpoint, once that is removed it forces IPv4 and the issue is gone.
I've also tested using Amazon S3 and Google on IPv6 and the same issue happens.
It requires closing and opening the app until it works again to fix it.