There are 40+ APs deployed in the facility (primarily AP650, some AP622), adopted by VX9000. WiNG 5.8.3.1.
In this particular room the AP650 was replaced with an AP7532 in order to see if the source of the issue was the AP (and client is going to replace 650s with 7532s over time anyway).
Users are complaining of being disconnected from wireless (network disappears), despite being right under the AP.
The AP did not reboot, did not loose connectivity, and did not un-adopt at any point.
It is happening only in a specific area (room), hence the replacement of the AP.
As I was writing this, I noticed the %RADIO-4-RADAR_DETECTED detected in the log, so it appears as if this particular AP is the only one providing signal in this area and it got knocked off channel because of a radar signal.
But I would think that the clients would have roamed onto 2.4GHz channel at this point, and not completely disconnected.
Note to all: use only non-DFS channels if there is a single AP providing coverage, or add a second AP on a different channel.