Nighthawk R7800, no 80 Mhz Bandwidth

Thank both of you for your suggestions.  See the following:

I do have 5 GHz neighbors but their power levels (signal strength) are low relative to my output (if this was a neighbor issue I would expect the Arris router to be affected also?).  The neighborhood 5 GHz spectrum is not crowded.  My Arris router uses channel 36 and the Netgear router uses channel 149 so there is a wide channel/frequency separation.  Also there is no channel overlap with others using the channels.  In further trying to eliminate the possibility of interference, I separated the routers by about 20-25 feet with two walls in between.  Still no change; still a 20 MHz channel.

I downloaded WinInfoView and it confirmed what my Android Wi-Fi analyzer said, the R7800 was transmitting 5 GHz at 20 MHz bandwidth (why would my range extender transmit the R7800 5 GHz signal at 80 MHz?  I would think the range extender would follow whatever the router was doing).  I wish I knew more about these things.

I also checked the Netgear web site and confirmed my firmware was up to date.

Lastly I visited the Voxel web site and downloaded what I think is the latest version of their R7800 firmware (R7800-V1.0.2.111SF).  I am hesitating to install it (cold feet) because I do not want to turn my router into a door stop. Admittedly, I can be "all thumbs" with such things. I have to give this some more thought.

This may be a hardware issue and not software? I believe the R7800 uses a Qualcomm radio module and that is the device that creates the 80 MHz path.  Maybe that is defective?

In any case, the router seems to be doing well for my purposes and this issue is, at this point, an academic one.

Lastly, I took Michaelkenward's note "Just another user with time on their hands" to be pointed at me.  Sorry, my mistake, even though I am retired and do have time to research these things that interest me.