Windows Server 2012 Hyper-V stuck at stopping. Computer will not restart nor shutdown

I have a major problem with Windows Server 2012. If a VM is stuck at "Stopping", it is impossible to reboot or shut down the machine. During the shutdown process Windows goes to the screen which says shutting down Hyper-V Service, and it gets stuck there. I tried letting it run for 40 hours to see if it would eventually shut down. But it did not. Windows was still stable since the round dot animation was still spinning.

This problem arose after I plugged in new Network Adapter to the motherboard. I tried changing the virtual switch to the new adapter, but I cannot remove the existing virtual switch. The Windows error says the following: "Error applying Virtual Switch Properties changes. Failed while removing virtual Ethernet switch. ... The system cannot find the file specified. (0x80070002). ... "

So my problem is definitely a Hyper-V bug related to the network adapter.

Does anybody know how to fix this?