Sorry I got slammed by work last couple of days and didn’t check back.
I wonder if it could be asymmetrical routing by your ISP? You mentioned your setup was okay before but it doesn’t work since you changed location.
I think your friend with the UniFi network has a static IP. Can you try traceroute to their IP and see if the route is similar to the one taken by their ISP? I’m not sure if this is how you’d test for asymmetrical routing but if nothing else the symptoms sound similar.