Ok, I found the problem. Obvious really, but so is any problem like this until you know the answer.
I installed Mosquito MQTT on Home Assistant through the GUI add-on tool, set it up, and set up most of my MQTT devices, and they all worked just fine.
When I tried to connect the Open Garage Units (I have 3 of them) they all started having the issues described above.
The MQTT log showed multiple entries of:
New connection from 192.168.1.161 on port 1883.
Socket error on client <unknown>, disconnecting.
New connection from 192.168.1.161 on port 1883.
Socket error on client <unknown>, disconnecting.
New connection from 192.168.1.161 on port 1883.
Socket error on client <unknown>, disconnecting.
Not really obvious what was going wrong.
I thought first it was the way Home Assistant handled the looping from some github posts. But wasn’t it at all.
How I solved it:
I intentionally gave one of my Open Garage devices the wrong IP address for MQTT. It continued to operate normally, and Home Assistant could see it. There was no slowdown in the web interface.
Looking more closely at the MQTT side of the house I found the problem:
}
],
“anonymous”: false,
“customize”: {
“active”: false,
“folder”: “mosquitto”
},
As soon as I realized that the default behaviour of Mosquito is “anonymous”: false I realized my mistake.
Setting “anonymous”: true, fixed the issue immediately.
Obvious in hindsight, but I am posting all the gory details here in case someone else with Open Garage and Home Assistant runs into the same problem, then they can google for my idiocy and fix their issue.