Android Samsung Galaxy - WiFi passwords not remembered

Background: Samsung Galaxy Note, Marshmallow 6.0: after a manual OS update the system does not remember WiFi passwords anymore.

What worked:
* Root the phone
* Install e.g. MiXplorer
* Go to root: /
* Click the three dots to show Options, select Show hidden
* Navigate to /system/etc/securestorage

* Find the hidden folder: .System.bin.wpa.supplicant or .System.wpa.supplicant
* Move (archive) this folder to another directory
* Reboot the phone

Added bonus: the WiFi passwords will be stored in plain text.
Short explanation why it works - see here.

What did not work:
* Manually editing wpa_supplicant.conf in /data/misc/wifi/
* Messing up with the file permissions or even deleting the whole /data/misc/wifi/
* Resetting the Network settings 
* Restoring Data.img from backup
* Trying to disable it by modyfing build.prop only
* Trying restoring via the otherwise useful WiFiConfigRestorer

Comments?