We have two nameservers as master-slave, and usually everything runs fine.
But in the last weeks we discovered two accounts where the default nameservers in the account settings were empty. This led to invalid DNS entries and DENIC errors which took us hours to hunt down.
I doubt that anybody edited these settings, so I am wondering if there is some systematic issue?
Without the ability to edit it as admin we would have probably never found the issue. So first the source of this issue should be fixed, though I have no idea what it is.