My guess is that the TI chip does support the 6mbps data rate as if its the one I think it is, it is a b/g/n chip. But keep in mind that if the signal strength is not great, it may not be able to connect at that rate.
If you drop the data rate and let the Sense connected again, can you look at it on the UniFi dashboard and see what rate it is connected at and what its signal strength is reporting?
In regards to Broadcast traffic, as mentioned elsewhere, you pretty much always need to allow broadcast traffic on if you are dealing with IoT devices that connect to your phone/ or other devices in your house directly and not via a cloud service. So a nest thermostat for instance doesn’t need broadcast traffic because you set it up by connecting to its generated wifi, and then once its on your network, all communication happens via the Sense servers. You want to change a temperature, you phone tells Nest servers and Nests servers tell the Thermostat.
Smart Switches, Smart plugs, smart fans etc… for the most part all communicate with your phone (and each other) locally on the network. Many offer enabling “remote access” which will then also connect them with a cloud service for remote management, but that is pretty much what it says. Used for remote usage (outside your home). But when you aren’t using the remote connection, the communication happened directly and your phone finds the device via broadcast.
This is why frequently you see people creating VLAN’s for their IOT stuff so that all that broadcast communication stays separate from the main data network. The downside of this is that without doing some specific routing trickery, often you lose that “internal” control unless you switch your phone over to the IOT network.
I do similar to you and set many “static” DHCP reservations, but I don’t quite agree with you on the DHCP lease time comment. Maybe your DHCP server is different, and I know its possible, but I’ve never encountered a consumer or prosumer DHCP server that sends out “infinite” DHCP lease times.
Mikrotik, Unifi and Barracuda F Series all honor the lease time of the DHCP server. The reservation is just that, a reservation, so that if the DHCP table is cleared, at least those reserved devices will always get their same IP’s. Halfway through the lease time, the devices should still be pinging the DHCP server for a renewal, but they just keep getting the same one.
I think Orbi specifically does some weird things as generically speaking, those settings should not have to be disabled to allow the communication that most IoT things need, with a giant exception for Sonos speakers. I can’t remember off the top of my head, but I know there are a few products out there that have called out compatibility issues with Orbi. All that being said, except for STP, DHCP and IGMP snooping also doesn’t need to be on for 98% of households.