Issue with the WPS connection

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### Basic Infos

Requesting additional consideration for previously unresolved closed issue

#### Hardware

Hardware

Hardware: ESP-12
Core Version: 2.3

### Description

Referencing [issue 3563 ](https://github.com/esp8266/Arduino/issues/3563).

ESP8266WiFiSTAClass::disconnect erases saved WiFi connection

@igrr --

I have been trying to stabilize your suggested workaround to store the old WiFi SSID and password and restore it if WiFi is unavailable. Unfortunately the WPS-generated credential continues to be lost intermittently. The only thing I can think of is that the device is interrupted somehow before restoring the previous WiFi credential. The result is that the device going permanently offline pending user intervention to press the WPS button on the WiFi endpoint. It's not a solution for a commercial IoT project.

Please reconsider your position on this. It is a big presumption that the developer/user wants to erase previous WPS-generated WiFi credentials if WiFi.begin() fails to connect to a WiFi endpoint. I cannot imagine a valid use case for this. I also don't see a stable workaround other than creating my own proprietary version of ESP8266WiFiSTA.cpp as per my original issue to prevent the erasure of WiFi credentials in the first place.

Thank you for your consideration.

### Settings in IDE

Module: NodeMCU 1.0 (ESP-12E Module)
Flash Size: 4M
CPU Frequency: 80Mhz
Flash Mode: qio
Flash Frequency: 40Mhz
Upload Using: SERIAL

### Sketch

SEE SKETCH FROM [issue 3563 ](https://github.com/esp8266/Arduino/issues/3563).