So no thanks to Ubiquiti support whatsoever, I discovered the issue with my inability to place video calls from one phone to the other. I was troubleshooting an issue after updating to the latest EA for network application, AP firmware and UDM Pro console, where suddenly many of my IoT devices are no longer able to get an IP address. They connect to the AP just fine but fail to get an IP. One of the suggestions was to turn off IPS, reboot, yadda yadda, but that didn't work, however... I had IPS turned on and I had enabled all of the attributes. This included VoIP, so I switched to "defaults," which turned off VoIP, and voila! What blows my mind is that "established and related" traffic and certainly internal traffic shouldn't be blocked by IPS, and yet that was the case. When I turned off the VoIP attribute, video calls started working. Nice job, Ubiquiti....