Ubiquiti has many other problems besides this. The worst is their vendor lockin, where even basic network operations are not possible if you happen to have any non-ubiquiti hardware in your network. You should stay away.
I ran UBQT hardware with mikrotik router and third party firewall. UBQT replaced old frankenstein hardware that had the worst channel management etc.
Everything got so much better, customers issues dropped to almost zero (sometimes was hundreds of issues a day)
We always had other vendor for part of the network, and that had no impact.
People are misinterpreting me, thinking I mean that it's not even possible to intermingle equipment. That is not the case.
The specific issue I ran into was that I had a non-ubuiqiti router and AP on my network, and there was absolutely no way to set firewall rules on the Ubiquiti gateway for any clients connected through the non-ubiquiti equipment. This should obviously not be a problem. The gateway provided those clients IP addresses through DHCP and they are in its ARP table, so it should be supported.