Serial communication on STM32F303 using HAL - Rx not working

Question

I am using an STM32F303RE Nucleo board connected to my own PCB to do RS-232 serial communications, and I can't figure out why this code doesn't work in certain circumstances.

I'm using HAL functions (HAL_UART_Transmit and HAL_UART_Receive) for my communications, using the USB connector on the Nucleo for usart2 and a 9-pin RS-232 serial port on my own PCB for usart1. Both usart configurations have been set up by HAL.

When I communicate (using a Putty terminal) using only the USB connection (usart2), the code works perfectly. When I use usart1 for Tx and usart2 for Rx, still no problems. When I use usart2 for Tx and usart1 for Rx, it also works fine.

The problem is when I try to use usart1 (which is my RS-232 cable) for both Tx and Rx. My processor transmits the initial data fine, but when it's time to receive the data, nothing makes it into the received data register. I have some code to simply echo back any received data on the transmit line, and nothing comes through in this configuration. Once again - the code works fine in every other configuration of usart1 and usart2 for both sending and receiving, but no Rx when I try to do it all on usart1 (RS-232)

Here is the relevant section of code I'm using. COMTYPE is set to either &huart1 or &huart2 (in the problem case, it's set to &huart1)

Main loop (received data used for switch statement in menu system):

    HAL_UART_Transmit(COMTYPE, prompt, sizeof(prompt), TIMEOUT);
    cmd_size = UART_getstr(command);

    cmd_num = parse_menu_input(command, cmd_size);
    converted = (uint8_t)cmd_num + '0';


    // error parsing command for menu selection
    if(cmd_num == -1){
        HAL_UART_Transmit(COMTYPE, parse_error, sizeof(parse_error), TIMEOUT);
    }
    else{
        menu_switch(cmd_num);
    }
}

Function containing Rx function and echo back (Tx) function:

int UART_getstr(uint8_t* command){

int x = 0;              // tracker for buffer pointer
int chars = 0;
uint8_t buffer;     // single char storage for UART receive

while(1){       

    // get single char from UART_Receive
    HAL_UART_Receive(COMTYPE, &buffer, 1, HAL_MAX_DELAY);
    // echo back function
    HAL_UART_Transmit(COMTYPE, &buffer, sizeof(char), TIMEOUT);

    // write value of received char to "command" array
    command[x] = buffer;

    // increment the number of valid chars
    chars++;

    // stop adding chars to command after [Enter] pressed
    if(command[x] == '\r'){
        chars--;
        break;
    }
    // correct for storing DELETE as char in buffer
    if(command[x] == 0x7F){
        command -= 1;
        chars -= 2;
    }
    else{
        x++;
    }
}
command[x] = '\0';

// return length of command buffer
return chars; }

I don't understand why the exact same code would work in 3 out of 4 circumstances, but not the 4th. I've checked the serial cable, and the rest of the RS-232 hardware functions fine when being used ONLY for Tx or ONLY for Rx. But the Rx seems blocked by something when trying to use RS-232 for both.

EDIT: Adding UART initialization code (generated by HAL):

/* USART1 init function */
static void MX_USART1_UART_Init(void)
{

  huart1.Instance = USART1;
  huart1.Init.BaudRate = 115200;
  huart1.Init.WordLength = UART_WORDLENGTH_8B;
  huart1.Init.StopBits = UART_STOPBITS_1;
  huart1.Init.Parity = UART_PARITY_NONE;
  huart1.Init.Mode = UART_MODE_TX_RX;
  huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart1.Init.OverSampling = UART_OVERSAMPLING_16;
  huart1.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
  huart1.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
  if (HAL_UART_Init(&huart1) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

}

/* USART2 init function */
static void MX_USART2_UART_Init(void)
{

  huart2.Instance = USART2;
  huart2.Init.BaudRate = 115200;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart2.Init.OverSampling = UART_OVERSAMPLING_16;
  huart2.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
  huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
  if (HAL_UART_Init(&huart2) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }

}