Fired up my first VM from the VM tab in Unraid, and that started fine. Later, I started my second VM, only this time from the Dashboard page. Instantly the VM's disappeared from the VM section on Dashbaord as if I didn't have any, and now in the VM tab of Unraid it also appears as though I have no VM's installed even though they are up and running.
After manually stopping one of the VM's (virsh shutdown "vm name"), then they appear again in the menu's.
EDIT: We believe that now this is only triggering when ALL your defined VM's are started. As a temporary workaround define a blank VM that you have no intention of starting.