stm32h753 rtc resets after power down (vbat is connected)

void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
  RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = {0};
 
  /** Supply configuration update enable 
  */
  HAL_PWREx_ConfigSupply(PWR_LDO_SUPPLY);
  /** Configure the main internal regulator output voltage 
  */
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
 
  while(!__HAL_PWR_GET_FLAG(PWR_FLAG_VOSRDY)) {}
  /** Configure LSE Drive Capability 
  */
  HAL_PWR_EnableBkUpAccess();
  __HAL_RCC_LSEDRIVE_CONFIG(RCC_LSEDRIVE_LOW);
  /** Macro to configure the PLL clock source 
  */
  __HAL_RCC_PLL_PLLSOURCE_CONFIG(RCC_PLLSOURCE_HSE);
  /** Initializes the CPU, AHB and APB busses clocks 
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE|RCC_OSCILLATORTYPE_LSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.LSEState = RCC_LSE_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM = 1;
  RCC_OscInitStruct.PLL.PLLN = 84;
  RCC_OscInitStruct.PLL.PLLP = 2;
  RCC_OscInitStruct.PLL.PLLQ = 4;
  RCC_OscInitStruct.PLL.PLLR = 2;
  RCC_OscInitStruct.PLL.PLLRGE = RCC_PLL1VCIRANGE_3;
  RCC_OscInitStruct.PLL.PLLVCOSEL = RCC_PLL1VCOWIDE;
  RCC_OscInitStruct.PLL.PLLFRACN = 0;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  /** Initializes the CPU, AHB and APB busses clocks 
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2
                              |RCC_CLOCKTYPE_D3PCLK1|RCC_CLOCKTYPE_D1PCLK1;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.SYSCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_HCLK_DIV2;
  RCC_ClkInitStruct.APB3CLKDivider = RCC_APB3_DIV2;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_APB1_DIV4;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_APB2_DIV4;
  RCC_ClkInitStruct.APB4CLKDivider = RCC_APB4_DIV2;
 
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
  PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_RTC|RCC_PERIPHCLK_USART3
                              |RCC_PERIPHCLK_SPI1|RCC_PERIPHCLK_SDMMC
                              |RCC_PERIPHCLK_ADC;
  PeriphClkInitStruct.PLL2.PLL2M = 1;
  PeriphClkInitStruct.PLL2.PLL2N = 25;
  PeriphClkInitStruct.PLL2.PLL2P = 4;
  PeriphClkInitStruct.PLL2.PLL2Q = 2;
  PeriphClkInitStruct.PLL2.PLL2R = 2;
  PeriphClkInitStruct.PLL2.PLL2RGE = RCC_PLL2VCIRANGE_3;
  PeriphClkInitStruct.PLL2.PLL2VCOSEL = RCC_PLL2VCOMEDIUM;
  PeriphClkInitStruct.PLL2.PLL2FRACN = 0;
  PeriphClkInitStruct.SdmmcClockSelection = RCC_SDMMCCLKSOURCE_PLL;
  PeriphClkInitStruct.Spi123ClockSelection = RCC_SPI123CLKSOURCE_PLL;
  PeriphClkInitStruct.Usart234578ClockSelection = RCC_USART234578CLKSOURCE_D2PCLK1;
  PeriphClkInitStruct.AdcClockSelection = RCC_ADCCLKSOURCE_PLL2;
  PeriphClkInitStruct.RTCClockSelection = RCC_RTCCLKSOURCE_LSE;
  if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
}
 

static void MX_RTC_Init(void)
{
 
  /* USER CODE BEGIN RTC_Init 0 */
 
  /* USER CODE END RTC_Init 0 */
 
  RTC_TimeTypeDef sTime = {0};
  RTC_DateTypeDef sDate = {0};
  RTC_AlarmTypeDef sAlarm = {0};
 
  /* USER CODE BEGIN RTC_Init 1 */
 
  /* USER CODE END RTC_Init 1 */
  /** Initialize RTC Only 
  */
  hrtc.Instance = RTC;
  hrtc.Init.HourFormat = RTC_HOURFORMAT_24;
  hrtc.Init.AsynchPrediv = 127;
  hrtc.Init.SynchPrediv = 255;
  hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
  hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
  hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
  hrtc.Init.OutPutRemap = RTC_OUTPUT_REMAP_NONE;
  if (HAL_RTC_Init(&hrtc) != HAL_OK)
  {
    Error_Handler();
  }
 
  /* USER CODE BEGIN Check_RTC_BKUP */
    
  /* USER CODE END Check_RTC_BKUP */
 
  /** Initialize RTC and set the Time and Date 
  */
  sTime.Hours = 0x0;
  sTime.Minutes = 0x0;
  sTime.Seconds = 0x0;
  sTime.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;
  sTime.StoreOperation = RTC_STOREOPERATION_RESET;
  if (HAL_RTC_SetTime(&hrtc, &sTime, RTC_FORMAT_BCD) != HAL_OK)
  {
    Error_Handler();
  }
  sDate.WeekDay = RTC_WEEKDAY_MONDAY;
  sDate.Month = RTC_MONTH_JANUARY;
  sDate.Date = 0x1;
  sDate.Year = 0x0;
  if (HAL_RTC_SetDate(&hrtc, &sDate, RTC_FORMAT_BCD) != HAL_OK)
  {
    Error_Handler();
  }
  /** Enable the Alarm A 
  */
  sAlarm.AlarmTime.Hours = 0x0;
  sAlarm.AlarmTime.Minutes = 0x20;
  sAlarm.AlarmTime.Seconds = 0x0;
  sAlarm.AlarmTime.SubSeconds = 0x0;
  sAlarm.AlarmTime.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;
  sAlarm.AlarmTime.StoreOperation = RTC_STOREOPERATION_RESET;
  sAlarm.AlarmMask = RTC_ALARMMASK_DATEWEEKDAY|RTC_ALARMMASK_HOURS;
  sAlarm.AlarmSubSecondMask = RTC_ALARMSUBSECONDMASK_ALL;
  sAlarm.AlarmDateWeekDaySel = RTC_ALARMDATEWEEKDAYSEL_DATE;
  sAlarm.AlarmDateWeekDay = 0x1;
  sAlarm.Alarm = RTC_ALARM_A;
  if (HAL_RTC_SetAlarm_IT(&hrtc, &sAlarm, RTC_FORMAT_BCD) != HAL_OK)
  {
    Error_Handler();
  }
  /** Enable the Alarm B 
  */
  sAlarm.AlarmTime.Minutes = 0x40;
  sAlarm.Alarm = RTC_ALARM_B;
  if (HAL_RTC_SetAlarm_IT(&hrtc, &sAlarm, RTC_FORMAT_BCD) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN RTC_Init 2 */
 
  /* USER CODE END RTC_Init 2 */
 
}

HAL_RTC_GetTime(&hrtc, &sTime, RTC_FORMAT_BIN);
HAL_RTC_GetDate(&hrtc, &sDate, RTC_FORMAT_BIN);
 
float subSecondsFloat = (  255 - sTime.SubSeconds );
subSecondsFloat = (subSecondsFloat /255);
subSecondsFloat = (subSecondsFloat * 1000);
 
year       = (uint32_t) (sDate.Year);
month      = (uint32_t) (sDate.Month);
day        = (uint32_t) (sDate.Date);
 
hours      = (uint32_t) (sTime.Hours);
minutes    = (uint32_t) (sTime.Minutes);
seconds    = (uint32_t) (sTime.Seconds);
subseconds = (uint32_t) (subSecondsFloat);
 
sprintf(usartSendBuffer,"\n%lu,%lu,%lu,%lu,%lu,%lu,%lu\n", year,month,day,hours, minutes,seconds,subseconds);
 
printf(usartSendBuffer);