In ubiquity gear you can “lock” devices to a specific endpoint. I suspect ultimately you would prefer to have failover available but at least for troubleshooting you can see how it connects to that specific AP. Similarly you could see the amount of clients connected to an AP on every frequency and WiFi version.
You can ban devices from all access points except one. That is not "locking" it to one, it's just preventing it from successfully connecting.
It will still try to roam, it will still cause issues.
A lot of the roaming logic is in the clients. Newer android and iOS versions have gotten better but there are tons of old and new devices with poor roaming logic and capabilities.
And actually debugging this unless you have a bunch of enterprise level kit, or know exactly what the failure you’re looking for is is absolutely impossible
I used Wireless Diagnostics.app on macOS ("Scan" window) and looked for the 2.4 GHz radio's MAC address which was nowhere to be found. But yeah, you have to have a hunch.
Thanks - I’ll try this. I have a problem where my kindle only downloads books in one room (but I can make purchases in any), and I’m pretty sure that it’s connecting to a different AP and doing something stupid in the process