Many STA-DISASSOC-REASON with reason=1 and ack_rssi=0

[jason_reich]

In our network of ZF7782 APs (mostly), we're seeing many log STA-DISASSOC-REASON with stable clients.  Most of our users are locked to specific APs and using Ubiquiti CPE devices, but we're seeing many disassociations.  For example in the support log I'm looking at now, I'm seeing about 150 in a 2 hour period on a single AP with 35 users.  Many DISASSOC appear to be after Channelfly changes, but not always.   Most of the STA-DISASSOC-REASON messages include "hint=send station disassociate", reason=1, and ack_rssi=0.  Example below:

Nov  3 03:31:32 NE FB daemon.warn Eved: STA-DISASSOC-REASON,nimac=80:2a:a8:7c:ea:9a,func=ieee80211_send_mgmt,line=4543,hint=send station disassociate,rx_rssi=44,ack_rssi=0,reason=1,freq=5765,chan=153,stats=(4202,585895,6341,7584346)

The MAC address in the line above is a user we're investigating, as they are seeing disconnect regularly (10-20 times a day), and then reconnect about a minute later.  Once they've reconnected, their RSSI values look good again, including values like ack_rssi 45 rx_rssi 45.

What does the "send station disassociate" mean; that the AP is initiating it?  If it was the AP, do the other logs below explain why?  I know that reason 1 is "unspecified", so that doesn't help me. 

What about the ack_rssi=0, what does that mean?

Is it typical to have some some disassoc after a channel switch?  Should we disable channel fly?

Any other suggestions of what is going on here, and how to avoid these clients dropping so often?

thanks in advance,

Jason.

PS: having troubles posting a longer log snippet; I'll try in a response.