XYZ Davinci Pro Network Problems

I've got a Davinci Pro 3D printer, and have identified an obscure network connection issue that I believe is associated with the printer firmware.

I use the Windows application to submit a job when connected to the home wifi network, then go out.
I then connect to the home network via VPN, and I can view the printing status ... no problem !
I return home, and reconnect using the home network and get a Timeout error when trying to look at the printing status.
I re-connect via VPN, and everything is fine.
Back to connecting via the home network, and no luck (Timeout again). 
I then wait and reboot the printer, and the home network works fine, until the next time I connect via VPN, of course.

I've managed to eliminate the XYZ software (and Windows) from the equation by using 'telnet printer 9100' - it either connects or times out.

This is the first problem report I've raised with XYZ, so here's hoping.