Multiseat - 19.10 and usb docking station

Hello all,
Using a Plugable UD-160-A laptop docking station (with a VGA output to the second monitor) connected via usb to my desktop (Gigabyte Aorus Master mb, single gpu) a second login screen is instantly available - a new seat! The second seat is fully functional for a couple of seconds before the session is terminated and the login screen reappears. Any suggestions on how to correctt this? I've not made any changes to the Ubuntu Mate 19.10 system or config files at this point.
Thanks, Greg