Multiple ESP12F conflict

I encounter a problem with two or more ESP12F's with WiFi manager library on them (GitHub - tzapu/WiFiManager: ESP8266 WiFi Connection manager with web captive portal)

Let's say there are 2 of them On both is the same sketch with different client SSID. On both, I go through the procedure of inserting SSID, PASS, etc so they connect to a local WiFi network. If they are on some 2 meters, everything is ok. If they are on some 10cm, there is a problem

One of them connects to a local network. The other tries, but fails every time. When I separate them, reset them, everything is fine. Only if they are close. And I have one setup that needs two of them on 10 cm.

may be you are getting interferences. You could try using setOutputPower() to reduce the power (I've never done it)

well if they are always at a distance of just 10 cm
why not use a wire?

Of if they should be wireless why not keep a distance of 2m?
best regards Stefan

As far as I can see, it restores back after a time. Gotta try it.

They are close, but they have to work separately.

Really ? Can’t you deal with only 1 arduino? They are pretty capable boards

It will be mounted in a wall. One on one side, and the other on the other side. They must work separately.

Almost regardless of the walls material the wall will reduce the signal strength. So you should do a test with some real walls.
If they are 10 cm with air inbetween the signal strength RSSSI might be -40 dbi. If you put a 10 cm wall between then it may vary between -50 dbi down to -80 dbi
best regards Stefan

The problem is while they are mounted on their places. Wall is made of gypsum board, so not much to reduce strength. This happens only when using the wifi manager library. I tried regular wifi scan sketches on 2 of Wemos, and they work fine in 10cm. The only project with this library when boards are close doesn't work as they should.

So maybe a solution could be using some other library with the same functionality as this WiFi manager.

I'm not familiar with the WiFi-manager ... looked it up
In the way I always do it
googling GitHUB Aduino "keyword"
In this case
googling GitHUB Aduino "Wifi manager"

found some "standard" WiFi-mamanger where the documentation says

This Documentation is out of date, see notes below
396 open issues

also found this WiFi-manager

has a lot of releases so I get the impression the Async-Wifi-manager is under continuosly development inspite to the "standard"-WiFi-manager.

best regards Stefan

Just put a foil of aluminum paper on the wall behind the module (on one side should be enough) so that waves from one module cannot go to the other module across the wall

This one I must try.