Regression from RDP level 1 to 0

Hello,

I'm trying to test RDP levels configuration on STM32H753.

Here is the code I've tested (on a Nucleo 743 with STM32CubeIDE):

int main(void)
{
 HAL_Init();
 SystemClock_Config();
 MX_GPIO_Init();
 MX_USART3_UART_Init();
 
 OBInit.Banks = FLASH_BANK_1;
 HAL_FLASHEx_OBGetConfig(&OBInit);
 RdpLevel = OBInit.RDPLevel;
 
 BSP_PB_Init(BUTTON_USER,BUTTON_MODE_GPIO);
 BSP_LED_Init(LED1);
 
 if ( RdpLevel == OB_RDP_LEVEL_0 )
 {
	/* Wait for User push-button press before starting the Communication */
	while (BSP_PB_GetState(BUTTON_USER) != GPIO_PIN_SET)
	{
 
	}
	// toggle LED1 to show RDP level
	BSP_LED_Toggle(LED1);
 
	// program OB
	HAL_FLASH_OB_Unlock();
	HAL_FLASH_Unlock();
 
	OBInit.OptionType = OPTIONBYTE_RDP;
	OBInit.RDPLevel = OB_RDP_LEVEL_1;
	HAL_FLASHEx_OBProgram(&OBInit);
 
	/* Start the Option Bytes programming process */
	if (HAL_FLASH_OB_Launch() != HAL_OK)
	{
		/* User can add here some code to deal with this error */
		while (1)
		{
			BSP_LED_Toggle(LED1);
 
		}
	}
 
 }
 else
 {
 
	 /* Wait for User push-button press before starting the Communication */
		while (BSP_PB_GetState(BUTTON_USER) != GPIO_PIN_SET)
		{
 
		}
		BSP_LED_Toggle(LED2);
 
		// program OB
		HAL_FLASH_OB_Unlock();
		HAL_FLASH_Unlock();
 
		OBInit.OptionType = OPTIONBYTE_RDP;
		OBInit.RDPLevel = OB_RDP_LEVEL_0;
		HAL_FLASHEx_OBProgram(&OBInit);
 
		/* Start the Option Bytes programming process */
		if (HAL_FLASH_OB_Launch() != HAL_OK)
		{
			/* User can add here some code to deal with this error */
			while (1)
			{
				BSP_LED_Toggle(LED2);
 
			}
		}
 }
 while (1)
 {
 }
}

The switch to Level 1 works fine. I can check that I am in Level 1 for example because the debugger doesn't work anymore and the LED 2 switches on. However the regression to Level 0 doesn't seem to work. I know the Flash is supposed to be erased but I cannot do anything after the "regression": cannot connect to a debugger or to STM32CubeProgrammer, no LED switches, etc...

Do you see something wrong in the code ?