Its been broken for a very long time now, I am surprised it has not been picked up )
RouterOS is not pushing the correct config in AUTO ( it should be pushing AT+CGDCONT=1,“IPV4V6”,“internet” ) in AUTO to the LTE Card, but is actually only pushing “IP” (which is ipv4) for the AT+CGDCONT LTE card config command . Accessible via RouterOS’s at-chat level commands.
Here is my take on the issue.
http://forum.mikrotik.com/t/lte-apn-auto-dual-stack-mode-hap-ax-lite-lte6-fg-621ea-seems-broken/181635/1