Remote Desktop (RDP) Rebooting problem

Have a contractor working for another company, connects to our network from home using his company provided laptop. Connection is made using Netilla and RDP, connects to a workstation in the building. Everytime the user tries to connect using Netilla/RDP, his initial attempt causes the workstation to reboot. After the reboot, he is able to attempt to login again and does so with no problems. Coming back in and logging into his physical workstation, not through RDP, forces it to reboot again.

Verified all settings with Netilla, and everything is where it should be. Not finding anything in the firewall or in the RDP settings to cause this. Suggestions ?