Random ARP Problems w/WiFi nodes

Thanks for the quick reply!

I live in a modest condo, 2x floors each roughly 20x40 ft, and a basement.  The main router is on the 2nd floor, with one satellite on the first floor roughly beneath it and about 10 ft to one side, and the second satellite is also on the first floor, roughly 20 ft away from the first satellite.  I then have several nodes (Raspberry Pis) in the basement almost directly below the second satellite, which seem to be the most trouble w/r/t 'incomplete' ARP, although I've had troubles with nodes on the first floor as well, and on more rare occasions the second floor (the latter usually after a power hit, which may happen a few times during the summer).

FWIW - BOTH RBW30 satellites are connected to the RBR40, and are NOT daisy-chained to each other, and the Backhaul status always says 'Good' for both.  I installed second satellite primary to try to insure good coverage in the basement.

There is another 2.4 GHz WiFi router on my 2nd floor, not too far from the RBR40, which I've set up for my step-daughter for security reasons (maybe about 20 feet away from the RBR40, which is also plugged into the BR500, so that she doesn't have access to the rest of my network through firewall rules -- not that I don't trust her per se, but I don't trust her not to visit nefarious sites and click on nefarious e-mails).  The NETGEAR BR500 router does not have any WiFi capabilities, and I do not have a WiFi router from the cable company.

However, there are "default cable" WiFi networks on both sides of my condo, and in several other attached units ... and by "default cable" I mean what you get free from the cable company, and not anything fancy (i.e., no extenders, no other meshes, etc., which I feel fairly confident about, because these are mostly older folks to come to me when they have IT questions, and I have been in most of their homes).

I have about a dozen or so WiFi networks that I can "see" on my 2nd floor Mac that is not far from the RBR40 with 3 or 4 bars (semi-circles?  ie., relatively strong singnal), and I definitely suspect WiFi saturation to be a likely culprit.  You've given me a few Advanced settings to try tweaking -- I currently have all defaults because I didn't want to mess with settings that I didn't fully understand -- so given this description, what settings do you think will most likely have a positive effect?

Again, I have about 50+ devices, including NEST thermostats and smoke alarms, about a half dozen Macs, about a dozen Raspberry Pis, a couple cell phones, and a few tablets.  The WiFi network is fairly stable, except when something gets rebooted, and then it sometimes takes other nodes some time to find it's MAC (ARP response).  Pinging from my 2nd floor Mac to a basement Raspberry PI is generally 10 - 20 ms, with an occasional 50 - 100 ms response (when I've run tests and ARP tables are populated, maybe 1% or less of pings to a basement RPi are > 25 ms, but always < 150 ms).

I thought Auto for channel might be the best option, since -- I thought -- it lets the router decide which are the best channels to use, but let me know which -- given that you know more about my configruation -- settings are most likely to provide benefit.  Or should I just start experimenting and see what makes a difference?

Thanks again,

Dave.