FS-220 add usb ethernet dongle for dual network access

[kerryp24]

Is it possible to use a USB 3.0 ethernet (gigabit) dongle on the USB port of the FS-220?
Actually, I have installed one and the TNAS Desktop showed two lans.
BUT, when I rebooted the TNAS, it sat there spinning for a while and when I tried to reconnect the desktop, it failed.
I tried using the TNAS PC app and it couldn't find the box either.

When I shut down, removed the dongle and powered up... all was fine.

Anyone have any thoughts or advice?
e.g. is there a way to tell the box what is the main ethernet lan to use?

TIA