Maybe check the ARP table for 10.0.0.41 to see if there is an entry with a MAC that is not the VM Computer. If you get a MAC, cross reference with manufacturer, see if it rings a bell with the customer. I had a firm add a Sony flat screen TV to the break room, the DHCP server didn't have the IPO address reserved so it handed it out to the TV. Damn thing wouldn't reply to pings unless it was turned on, so VPN phones would fail and oddball times.

And, I always have a flat screen monitor and keyboard with a touchpad in my van for headless servers

So glad you got it sorted out - hope that customer pays his bills to you!!