Resolved
We've put a fix in place, monitored it, and resolved this issue, all VMs are now be able to be stopped/started/created without any issues.
Investigating
We're currently seeing issues where the network isn't being applied on Startup. This is currently an issue for new servers and those where servers are Shutdown and Started via the Client area.
Reboots via the OS though appear to be ok. Updates will be provided as this is progressed.