Range extender between 2 Kuna outdoor webcams and my Quantum (Verizon) router

I bought 3 Kuna webcams.  All 3 are the same model - each has a camera, microphone, a speaker, and a lamp that I can turn on/off via the app.  Two are installed outside my garage (sconce lights) in the front of the house.  One is for the rear deck.  These webcams run on 2.4GHz only.  The wireless router is connected to a coax cable near the back of the house.  The one camera on the rear deck works perfectly.  When I launch the Kuna app on my iPhone and see & hear (with ~2 second delay), what's going on.  That's the one that doesn't go through the range extender.

The EX3700 is set up for DHCP.  The router assigns it an IP4 address, and I can log into the range extender.  No problems there.  The router is running both 2.4GHz and 5.0GHz.  The router can do a 'check' of the local RF traffic, and recommends the optimum 2.4GHz and 5.0GHz channels.  So, I set my router to:  2.4GHz Channel 1, 5.0GHz Channel 153.  I bought the router from Verizon.  The brand is Quantum and has devices (wired & wireless) running with no problems for a couple years.  It's set up with port forwarding so I can see my Ring camera.

The 2 cameras mounted outside my garage have signals that have to go through brick, etc.  I connected the EX3700 to my router via WPS.  I downloaded the firmware update.  It's now running V1.0.0.84_1.0.56.  The EX3700 is plugged into an outlet near the front of my house.  I consistently have green LEDs displayed on the range extender for both:  Router and Device.  I tried configuring FastLane on the EX3700.  Same problem.

When I launch the Kuna app, trying to view either of the 2 cameras outside the garage will (1) take a minute to display on my phone, and (2) it's just a static image with no audio.  Then, the image pixelates.  My best guess it that the signal from the 2 cameras attenuates too much (through brick) to send realtime audio & video.  All 3 cameras detect fast changes in light level (similar to Ring cameras) triggering a motion alert to my phone.  That part works. But (I think) that's because it's only a quick pulse.  It's the multiple frames/second & audio that are the problems.

Is the best course of action:  another range extender to be plugged inside the garage?  Should it be another EX3700, or should it be another model?  Can these be configured to work:  Cameras --> EX3700#1 --> EX3700#2 --> Router?  I haven't tried setting up a static IP for the range extender and removing that IP from the IP pool in the router, but I don't think that would help.  I have tried moving my EX3700 into the garage (closer to the cameras, further from the router).  The router LED on the EX3700 goes amber.  (Device LED remains green).

Questions and/or Suggestions.