Unexplained Wi-Fi Issue with EA8500

My normal setup: Spectrum Cable Modem, connected to a Linksys EA8500 Router (main router, controls DHCP), connected to a Linksys EA6500 in Bridge mode. They each have 2 SSIDs, one for 2.4 and one for 5Ghz...so 4 SSIDs, total (no guest SSIDs). The Channels server is wired directly with the EA8500.

I have four Firestick 4Ks, with two being wired. The two that are wireless hook up to the EA6500.

This setup works great, with an average of 350mb back to the channels server.

I was trying to rearrange some things, last night and trying to set up the EA8500 to be more central...I basically swapped physical locations, but kept the same networking...cable modem to 8500 and that to the 6500. I restarted everything on the network.

I fired up the wireless Firesticks and connected them with the 8500. Everything seemed to work just fine (Netflix, Amazon, Disney+, HBO Max, Bally Sports), until I started Channels...it took a really long time to load and then the guide was mostly blank. I tried a speed test, back to the server, and it started about 50mb and quickly died to less than 5. Tried that several times, same results. Stations that would play took a long time to start and then played only for a moment.

So, I thought I had something wrong, but everything I tried to do that had those Firesticks connected to the 8500 had the same result.

I took the 6500 completely out of the loop and setup just the Cable Modem, 8500 and the Channels server...restarted everything...still the same result.

I put everything back the way I originally had it and it works just as good as ever.

Not the end of the world, but I just cannot get Channels (and only Channels) working with the EA8500.

Has anyone had a similar experience? I read about a lot of wifi experiences, but did not see quite this one. The only hit I had about an EA8500, was my own post from a year and a half ago...and it seemed to work, then.