Store the ADC stream on µSD Card without loss on STM32H743ZI

Question

I am working on a project in which I have to store the datas of an ADC Stream on a µSD card. However even if I use a 16 bits buffer, I lose data from the ADC stream. My ADC is used with DMA and I use FATFS (WITHOUT DMA) and the SDMMC1 peripheral to fill a .bin file with the datas.

Do you have an idea to avoid this loss ?

Here is my project : https://github.com/mathieuchene/STM32H743ZI

I use a nucleo-h743zi2 Board, CubeIDE, and CubeMx in their last version.

EDIT 1

I tried to implement Colin's solution, it's better but I have a strange things in the middle of my acquisition. However when I increase the maximal count value or try to debug, the HardFault_Handler appears. I modified main.c file by creating 2 blocks (uint16_t blockX[BUFFERLENGTH/2]) and 2 flags for when adcBuffer is half filled or completely filled. I also changed the while(1) part in main function like this

    if (flagHlfCplt){
          //flagCplt=0;
          res = f_write(&SDFile, block1, strlen((char*)block1), (void *)&byteswritten);
          memcpy(block2, adcBuffer, BUFFERLENGTH/2);
          flagHlfCplt = 0;
          count++;
      }
      if (flagCplt){
          //flagHlfCplt=0;
          res = f_write(&SDFile, block2, strlen((char*)block2), (void *)&byteswritten);
          memcpy(block1, adcBuffer[(BUFFERLENGTH/2)-1], BUFFERLENGTH/2);
          flagCplt = 0;
          count++;
          }

      if (count == 10){
          f_close(&SDFile);
          HAL_ADC_Stop_DMA(&hadc1);
          while(1){
              HAL_GPIO_TogglePin(LD1_GPIO_Port, LD1_Pin);
              HAL_Delay(1000);
          }
      }
  }

EDIT 2

I modified my program. I set block 1 and block 2 with the length of BUFFERLENGTH and I added a pointer (*idx) to change the buffer which is filled. I don't have HardFault_Handler anymore but I still loose some datas from my adc's stream. Here are the modification I made:

// my pointer and buffers
uint16_t  block1[BUFFERLENGTH], block2[BUFFERLENGTH], *idx;
// init of pointer and adc start
idx=block1;
HAL_ADC_Start_DMA(&hadc1, (uint32_t*)idx, BUFFERLENGTH);
// while(1) part
while (1)
  {
      if (flagCplt){
        if (flagToChangeBuffer) {
            idx=block1;
            res = f_write(&SDFile, block2, strlen((char*)block2), (void *)&byteswritten);
            flagCplt = 0;
            flagToChangeBuffer=0;
            count++;
        }
        else {
            idx=block2;
            res = f_write(&SDFile, block1, strlen((char*)block1), (void *)&byteswritten);
            flagCplt = 0;
            flagToChangeBuffer=1;
            count++;
        }
      }

      if (count == 150){
          f_close(&SDFile);
          HAL_ADC_Stop_DMA(&hadc1);
          while(1){
              HAL_GPIO_TogglePin(LD1_GPIO_Port, LD1_Pin);
              HAL_Delay(1000);
          }
      }
  }

Does someone know how to solve my matter with these loss?

Best Regards

Mathieu