WAX630E periodically deauthorizing/dropping connections

About every 20 minutes or so, my network monitor shows a dozen or so wireless devices on the WAX630E lose their connection (ping fails).  Within a minute or two they are all come back online.  When this happens, I can see in the WAX630E log a series of messages about deauthorizations and disconnections.  This AP was seemingly working fine and I didn't experience any of these drops previously.  This all seemed to occur about the time I added a 4th SSID on a different VLAN about a month ago.  Is anyone having any issues with their WAX630E dropping connections regularly?  Any advice on what to investigate?  See image (can't attach the full log)