RBR50 providing poor (<5mbps) download speeds to entire network (both wired and wireless)

I promise you this is an issue with firmware.  I have similar problems.  I have an RBR50 with 3 satellites (4000 sq ft home).  I have fiber with 1 GB service.  PC is hardwired to router.  When I first set up network, I was clocking speeds on PC that were equal to speeds clocked when hooked up directly to ONT; anywhere from 866-940ish MBPS everytime.  Over wireless I would get speeds of 380-550 MBPS depending on location within the home.  Following firmware updates (i'm currently running V2.5.1.8) my PC now clocks no higher than 200-240 MBPS and my wireless speeds are no better than 40-90 MBPS.  

I have been round and round with Netgear.  I've changed channel settings to 11 for 2.4 GHz and 40 and/or 48 for 5 Ghz.  I have reflashed router with both current firmware as well as previous versions and done multiple factory resets.  All to no avail.  Netgear is sending a new router, but I doubt that will solve anything because I hooked up a previous RBR50 (I initially bought 1 router and 1 satellite bundle and needed more coverage so I bought 1 router 2 satellite bundle from Costco and added additonal satellite from previous system).  On a whim, I went ahead and hooked up previous router and was clocking speeds hardwired to router with PC as I did with initial setup.  Here's the kicker, in order to for firmware updated satellites to sync with old router, the router has to be upgraded to latest firmware.  And that's where it all goes to hell.  Once I did that, same awful throttling of speed as stated above.  And when I reflash firmware back to old and do factory reset, the speeds don't improve.  Has to be something lingering from firmware upgrade causing the issue.  At any rate, if I can't get a solution soon, I'll be moving on to a different network....Orbi has been a tremendous headache and waste of time.  System is trash with current firmware no matter what settings you use.