IWDG disable during Sleep/Stop

Hello.

I am running STM32L412 microcontroller in low power GSM design. All works great, but I would also want to add watchdog just in case.

I am in STOP2 mode most of the time, and I am waiting for interrupts from GSM module or MEMS IRQ

I configured IWDG for 30s reset, I reload it just before sleep that takes 4 minutes (IWDG = 30s).

In boot I also RESET IWDG_STOP and IWDG_STBY bits based on reference manual, I also check FLASH OP register to see if bits are truly zeros and they are.

BUT I still been RESETED in STOP2 mode, while it should NOT HAPPEN based on my limited understanding.

Any ideas what I am doing wrong ?

 FLASH_UNLOCK();
 FLASH_OB_UNLOCK();
 CLEAR_BIT(FLASH->OPTR,FLASH_OPTR_IWDG_STOP|FLASH_OPTR_IWDG_STDBY);
 
 FLASH_OB_LOCK();
 FLASH_LOCK();
 
 
void FLASH_UNLOCK(void)
{
 if(READ_BIT(FLASH->CR, FLASH_CR_LOCK) != 0U)
 {
 FLASH->KEYR = FLASH_KEY1;
 FLASH->KEYR = FLASH_KEY2;
 if(READ_BIT(FLASH->CR, FLASH_CR_LOCK) != 0U)
 {
 //return 1;// ERROR
 }
 }
}
 
void FLASH_OB_UNLOCK(void)
{
 if(READ_BIT(FLASH->CR, FLASH_CR_OPTLOCK) != 0U)
 {
 FLASH->OPTKEYR = FLASH_OPTKEY1;
 FLASH->OPTKEYR = FLASH_OPTKEY2;
 }
 else
 {
 //return 1;// ERROR
 }
 //return 0;
}