Another possible bug I ran into:
I had ns1.company.com and ns2.company.com running. They work. I even added the ipv6 records for them, because it's working dual stack now. dig @ns1.company.com website.com A
works as it should, both ipv4 and ipv6.
I also added the new DNS roles for ns3.company.com and ns4.company.com on other servers. However, these refuse to return any values when queried with dig @ns3.company.com website.com A
Can anyone else confirm this? The new DNS roles don't seem to be participating in the pool, while the old ones are working fine, updating with new entries etc.