R7900 with EX8000 extender issues

I have the R7900 wireless router with the EX8000 set up as a range extender.  I have Smart Connect turned off, with both channels separated.  The extender drops the network connection multiple times a day, sometimes for less than a minute before it reconnects, at times it could take up to 10 minutes to reconnect.  When this happens, the lights on the extender and the router are working as they should but there is no wifi connectivity. 

I have a Guest network (on both bands) that are not going through the extender and those are very stable and never loses connection which is why I am pretty sure there is something wrong with the Extender.  Both units less than 2 years old.  

I have done factory reset on the extender (pretty much every other week) but it does not help.  The extender is located about 20 ft from the router.  I did not do any special (advanced) configuration on the router, other than the straightforward set up per instructions.  The channels for the 2.4GHZ network is Auto selected and the 5GHZ has a range for each of the bands.  Again, setup for Guest network is identical.  

I am at my wits' end.  I wanted a stable and extended connection and I thought that buying the top of the line Netgear suite for a 2 story home will do the job.