I put a call into support and had them look at my maps, survey data, and of course - the settings.
He came to the conclusion that I had some definite overlapping of AP's running on the same channel. And that the signal power is way too high (cranked full). I had a bit of mis-understandings with the settings. That is, when I put channel plan to "Auto" I had thought that this meant the AP will device on what channels to run with (thinking it would make on the fly intelligent decisions). But that is not the case.
He suggested that I wait until a maintenance window and then (for both radios):
- Set Auto Tx Power Ctrl (ATPC) = Checked/Enabled
- Under Advanced > Dynamic Channel Selection, set from Monitor to Active Modes
- Wait at least one hour, more if possible
- Set Auto Tx Power Ctrl (ATPC) = Unchecked/Disabled
- Under Advanced > Dynamic Channel Selection, set from Active to Monitor Mode
If problems persist, he also suggested that I fiddle with the settings that will force-disconnect a client who is remaining connected to a terrible connection and refusing to roam (aka Sticky clients). That is, setting "Probe Suppression" to Checked/Enabled, setting Force Disassociate to Checked/Enabled, and then changing the RSS Threshold [dBm] to somewhere around -75 (default is 90, which seems way too high ... at least in my environment).
I plan on making these changes tonight when the facility is closed and I will report my findings!