There is a lot of discussion on this in this community. The short fix is that you'll find you have issues on 2.4ghz wifi, so if you can switch to 5ghz, that helps. Also, newer routers are worse than older routers it seams. Using your Maestro is like streaming video. :) if there are a lot of 2.4ghz wifi signals around, you'll have to deal with the congestion they cause as well. Another reason to move to 5ghz (you'll need a dual band access point).
For the time being, reduce your waterfall updates (under the display menu - bottom left) and see if that helps.
I have been testing some TCP/IP over AC (house wiring) by TP-Link. They have allowed me to put new Wifi access points in weak areas without pulling CAT 5 and they work very well. I have not notice any HF noise on them. https://www.amazon.com/TP-LINK-Extender-Powerline-Wireless-TL-WPA4220KIT/dp/B00HSQAIQU/ref=pd_sim_sb... ... this is one example.
One possible issue is that Maestro and the 6000 will autonegotiate a 1Gb/s speed if they can, but the router and/or cabling may not be good enough to sustain the high speed with low error rate. I fixed my installation by putting in an older/cheaper 100 Mb/s switch for the radio and Maestro. That reduced error counts to zero.
It would be helpful if we had the option to manually lower the Ethernet rate.
73 Martin AA6E
One thing that can be done is to eliminate using the R6400's ports (aside from the one needed to go to the switch), use a quality gigabit switch. I upgraded my main switch to the Netgear GSS116E, very fast and stable.
My R6700 wireless to the Maestro is fast and stable anywhere in my relatively small 1700sqft 3 story house (including the basement where the R6700 is) and upstairs I get full strength green and rarely above 4ms, most of the time it shows 1ms. Wired to my switch it's almost always <1ms, I may see it jump to 4ms.