Random temporary loss of connectivity

We have one ePMP AP1000 w/ GPS that randomly loses connectivity with the SM's.  The clients never disconnect from the registration table and will start passing traffic without any intervention on our part.  The AP is not losing GPS, as all SM's stay connected.  We are running firmware 3.5.1, both banks are updated and the GPS chip is up-to-date.  We discovered this when one customer called reporting sporatic service.  When the customer losses connectivity, the SM is in the registration table but cannot be pinged from the AP.  We can deregister the AP and as soon as they come back all is working.  We have checked, there are no dupicate MAC addresses or IP addresses.  It is like there is an IP confliction, however then all the sectors on that subnet would be affected.  I am too the point to swapping the AP, but I hate to if it is something simple. 

I just saw this:


This may be the same issue.  

Rolled back to 3.4.1 and the random connectivity issue seems to have stopped.  It has now been 1 day 19 hours with no drops.  We were having several per hour.  So maybe something in the 3.5.1 firmware.