I have certain stationary devices that I would prefer not roam or be forcibly moved to another access point for load balancing. 
 

For example, I have a 4K TV within 8 unobstructed feet of a Deco M4R.  The Deco M4R is connected via eithernet backplane to a Deco M5 on an entirely different level, across the house.  When the TV connects to the M4R, the signal strength is excellent and the TV's speed test yields 35Mbps.  It is infuriating to me that the TV and/or the Deco mesh seem to prefer the TV be connected to the M5, which has only fair signal to the TV and yields ~20Mbps.

There should be some way to set affinity for devices to access points (even in access point mode).

I have tried the "Mesh Technology" toggle in the client settings, but even with that disabled, my TV migrates back from the strong signal AP to the weak signal AP.