TVs keep losing WiFi Connection

Hello, this is my first post, so please excuse me if I give too much or too little information.

A few months ago we decided to leave behind Cable (we were with Xfinity) and try streaming.

I had some experience with a small Roku TV I use in my exercise room, so I thought new Roku TVs would be perfect.

We have a big house (almost 5000 sq ft) and four adults living here, so I purchased three new Roku TVs.

Two of these:  https://www.amazon.com/dp/B0C92VCZ48?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

and one of these:  https://www.amazon.com/dp/B0CLFFXNML?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

We had them connected to our WiFi network through XFinity for a few days, and then we had Ezee Fiber installation. They use these Eeros for their system, so we have two of these, one at the main hub (in the room with the 65" TV) and one downstairs in the entry way (to try to serve the other two TVs, which are in rooms 30-40' away).

All three TVs seemed to have no trouble staying connected to the old Xfinity wifi network (I used eero 6's to spread the signal, but I had six of them so they were right next to the TVs)

Once we got the new ezee fiber service, all three TVs connected to the new wifi network (named the same as the old network) just fine. HOWEVER, the problem comes as you watch a show. Every few minutes (sometimes every hour, sometimes 30 minutes, sometimes over and over every 5-10 minutes) the wifi will drop and the spinning will happen. Sometimes it will come back on its own; other times the message "No connection: Connect to the internet now..." will pop up. This happens on all three Roku TVs, even the one in the room with the hub, so I really don't think it's a signal strength thing.

At first, I did troubleshooting by reconnecting the WiFi as instructed on the screen. I did this several times and taught everyone how to do it for themselves, but we all got sick of that very quickly.

Then I did hard restarts of the TVs. No help.

Then I tried system updates. No help.

Then I tried turning everything off for an hour—all TVs unplugged, unplugged the modem.  Restarting everything seemed to help a little at first, but not really. Still, as one of us watches a show, the signal will drop.  We've figured out that just waiting patiently for a while it will come back, sometimes in a few seconds, other times a minute or two.

Getting desperate I've called ezee fiber for help. They are very nice, but their suggestions to turn everything off (hard system restart) didn't help. I'd already tried that, but I did it again and still nothing. 

Finally, they suggested renaming the network. I really didn't want to do that, but I finally caved and tried it. That involved reconnecting every device in this house. I realize now I shouldn't have done it, because, of course, it didn't help at all and was a HUGE pain.

Ezee Fiber has given up trying to help me now. The guy says he's stumped.

My next thought is to replace the eero Max 7s with some other mesh wifi system. Ezee Fiber says the 7 is necessary, but there seem to be other options available, so I could potentially try that.

The only other thought I have is to complain to Amazon about defective TVs and try to return them or get Asurion to help me troubleshoot. I haven't tried them yet, but I'm at the end of my rope.

Does anyone have any suggestions for things I could try before getting to the return stage?

I want to like Roku, but at this point I'm seriously regretting my purchases.