Samsung Galaxy S4 (i9505) keeps forgetting wifi passwords

Everything was fine when my S4 was running the stock everything.
I flashed the 5.0.1 firmware from sammobile (OTA was not available in my region).
Now the problem starts that the cell keeps losing the wifi passwords of all routers (wingle devices, routers, hotspots). Always after restart, sometimes even without restart.

THINGS TRIED SO FAR
I did *#0011# - WiFi - Turned OFF power save mode - no luck
Switched of "Smart Network Switch" - no luck
I tried flashing different ROMs from sammobile, but the problem still persists.
I search some forums on modems and assumed that LTE/Wifi fix modem might be causing problem, so i try different modems, still no luck
ROMs tried:
I9505XXUGNG8_I9505YXZGNH2 - 4.4.2
I9505XXUGNG8 - 4.4.2 Tmobile (it got lollipop OTA, but problem persists)
i9505XXUGNK2 - 4.4.2
I9505XXUHOJ2 - 5.0.1
I9505XXUHOH2 - 5.0.1

Different modems tried on 4.4.2:
I9505ZHUFNB3_WIFI_FIX
I9505_XXUFNA5_WiFi_FIX
I9505_XXUGNK2_WiFi_FIX
I9505XXUGNK4_LTE_MODEM
I9505XXUHOE2_WiFi_FIX
GSM_Modem_XXUFNB8_and_LTE_Modem_XXUFNB8
I9505_XXUBMH1_MODEM

Any help in this regard will be highly appreciated. My personal preference is KITKAT OS.
My current details
Model: GT-I9505
Android version: 5.0.1
Baseband version: I9505XXUHOJ2
Build number: LRX22X.I9505XXUHOJ2
Kernel Version: 3.4.0-5978264