TV Mac target problem(s)

I have used TV for many years to resolve problems on our home Macs (Pro and Mini running ElCapitan, TV 13 on them set for unattended access) while I'm away at work on a PC. Until recently my work PCs were Win7 and I never had a connection problem. Recently I had to update the PC to Win10. The first time I then used TV to connect home I found that the Macs' screens opened fine but were frozen and unresonsive like a still photo. When I got home both had the "Thank you for using TeamViewer" window up.

I've uninstalled & reinstalled TV 13 on both Macs but no change. I rolled back TV on the PC from 14 to 13 with no change.

Much to my surprise when I installed TV on my iPhone I get exactly the same result when I connect to the Macs - even when I take it off the work WiFi and use cellular. That pretty much localizes it to the TV install on the Macs. Do I need to do a nuke & pave uninstall using something like AppZapper before I reinstall TV 13?

Update: Testing at home, TV 13 on another Mac connects just fine to the two other Macs. Incomming LAN connections is set to deactivated, so it should not be connecting directly through our home network.