Apologies in advance for likely using incorrect terminology but I'll describe my issue best I can!

About 8 months ago, I setup AXE75 as my main router connected to my ATT fiber modem/router.  On the ATT modem I setup IP passthrough and turned off the SSIDs .  I then added a few extenders using EasyMesh "adding satellite devices" and I was sort of surprised but everything went pretty well....up until a week ago.

I have an oddly TALL house and the only place I can keep my modem/router (per ATT) is in a back structure about 50 ft from the main house. This is why I wanted to setup a stronger network and get away from what was a poor ATT WiFi "mesh system" which just wasn't strong enough and gave me constant problems.

Problem: About 7 days ago the "internet went down" (screamed at me by teenagers).  The "Internet light" on the router had turned red. I restarted the AEX75 and after a few minutes it turned green again, all was back. 

BUT this is now happening every day at random times, about twice a day.  I cycled the router power each time but obviously not a permanent solution.  So I completely reset EVERYTHING and started fresh again.  All looked as it should and worked for about 8 hours, then the same problem came back.

There is no firmware update available for my router as far as I can tell.  I don't have any idea how to come up with a solution at this point.  Could it be the ATT modem that is glitching or something? The modem appears to be running 100% with no issues, every time I checked it when this problem happened, the modem seemed fine. But I don't know how to know for sure or solve this problem in general.

Any help to restore my sanity and peace in myhouse....PLEASE and THANKS in advance!