I am a bit confused about your environment. Could you please clarify more details?
>>There is a HyperV setup for the Domain Controller, a HyperV for an SQL Server. There are 4 network adapters setup in all. One is disabled. One is assigned to each HyperV and one is setup for the Host workstation.
Based on my understanding, you have a VM set up for the DC and a VM set up for the SQL server. You have four physical network adapter, one is disabled. One is assigned to VM as external virtual switch, one is for hyper-v host. Is that right?
Please feel free to let me know if my understanding is wrong.
If my understanding is correct, your NIC which is used by the Hyper-V external network should not have an IP in the host OS. So please uncheck box of your external switch to not allow the host to use the NIC.
Then check if the error was gone.