Workaround to take back DC VM from CSV.
4. Once remove, go to Storage and you will see the disk located in Available Storage. Assign a Drive Letter and copy the VHD out.
This is the simple trick to recover the DC VM which is inside the CSV. Hopefully, you can now create the a new VM and point towards the copied VHD then start the Domain Controller. Once the DC is up, then you will be able to start the Hyper-V Failover Cluster.
Just to remind again, you should have at least 1 DC not in CSV or run in the physical server.