The UDM SE has a bug where if you max out 1 Gbps for a bit, at some point the WAN interface is going to crash and you have to either 1) restart, 2) unplug and replugin the cable, 3) restart the interface the WAN port was on.
This bug has existed for over a year, with no fix in sight.
Unifi's quality is dropping day by day. I'm convinced they don't use their own networking tools.