Not able to see ESP32 AP in busy wifi environment - any ideas why?

[globoy]

I have an ESP32-based device advertising itself as an access point.  Setup is using the default Espressif wifi library configuration with US channels (channel 1 / 100 mSec beacon).  In some places - for example an apartment complex with a large number of active wifi networks - clients cannot see the AP (clients tested: Linux, OS X, Win 10, IOS and Android).  Clients were near the device.  In less busy environments clients have no trouble seeing the device.

I also ran an experiment where I took an ESP32 dev board and loaded a simple wifi AP demo program using the ESP32 Arduino environment and saw the same result.  I did this as a check to make sure I wasn't doing something clearly wrong in my code which is using the IDF (not Arduino).  The dev board could not be seen in the apartment either but could be seen when moved to a less busy environment.

Other routers are being seen (for example I could find and connect clients to the apartment owner's xfinity access point).

The only thing I can think of is the beacon is getting stomped but maybe I'm missing something else.  Perhaps some RF device in the apartment building is misbehaving but I have a report from one customer in a different location that makes me think they saw the same problem.  Has anyone ever seen something like this?

Unfortunately I didn't think to do a channel assessment but will try that when I can get back for more testing.  And I'll try a different beacon period.