Good afternoon.  

I recently added an X55 V1.6 to my Deco mesh network as the main Deco.  I have three M9 Plus units for the rest of the house, due to architectural issues that limit signal.  The X55 is in the living room attached to the router.  my computer is about 10 feet away.  It is located under a desk, but has a cabled antenna that has almost direct line-of-sight to the X55.  However, the computer keeps switching to the other M9 units, despite the fact that they have weaker signal.  I have tried turning off beamforming and fast roaming, but it still will only connect to the X55 for only a couple of minutes before switching to another router.    

I can get it to connect to the X55 by shutting down all the M9s and then resetting my wifi on the PC, but within a couple of minutes of turning on the M9s, the PC has switched to one of them, with a weaker signal, and the requisite loss of speed.  I also see this behavior with my TV, which is literally 3 feet from the X55 router, with nothing in between.  I see this with several other things as well, such as my Pixel 6 phone and my iPhone.  

What can I do to stop this from happening?  It makes a major difference in the speed of my connection, often causing serious lag loading websites and while streaming. Is this possibly a bad router that I need to get repaired/replaced under warranty?