WN3000RP dropping connection

I have small issues (Until the wife's device fails).  The WN3000RPv2 will go along nicely for awhile, then internet gets slower, if I ping it, it starts dropping packet returns- 80%-90% in some cases. Then it will drop carrier totally. I have done a factory reset six times in the last two weeks.  And at this point, it will drop signal (Red light even on the extender, sometimes.) to a Dell laptop, a Kindle Fire tablet, a HP Laptop running Ubuntu 16.04. My phone also will drop carrier, the others in the family don't know (or care) if their devices are on phone system, or wifi, as the devices will change automatically.  I have tried to get it to connect with 5Gz, but it will not see the ATT gateway @ 5gz as this extender is not 5gz compatible.  I have replaced the gateway as standard issue from ATT, the extender is from ATT when the gateway was discovered to have a signal attenuation problem in the house. Currently, the WP3000 extender says it has 75-90% signal strength (compared to what, I don't know)  and I have it moved to the sofa in the living room.  The most stable (not 100% even, sometimes it will fail that, too) connection is through the ethernet cable.  At this point, what am I missing or any suggestions on settings?  I have changed channels multiple times, factory reset multiple times, changed as many things as I could. What else is there?  I am not helpless, but I do miss a few subtle things now and again. I have contacted ATT, they have directed me to Netgear. So a little suggestion would be helpful. Thanks.