nRF9160 Reboots when Accessing UART2

Question

I have a custom board with a GPS chip and trying to communicate via UART2 on a nRF9160 using NCS 2.1.2.

When I try to write to the UART, the board reboots with no error messages. This was working when I had it set to

UART0 but changing to UART2 started this issue. Any thoughts would be appreciated.

DTS:

&uart0 {
	status = "okay";
	current-speed = <115200>;
	pinctrl-0 = <&uart0_default>;
	pinctrl-1 = <&uart0_sleep>;
	pinctrl-names = "default", "sleep";
};

&uart2 {
	status = "okay";
	current-speed = <9600>;
   label = "UART_2";
	pinctrl-0 = <&uart2_default>;
	pinctrl-1 = <&uart2_sleep>;
	pinctrl-names = "default", "sleep";
};

prj.conf

CONFIG_SERIAL=y

CONFIG_CONSOLE=y
CONFIG_UART_CONSOLE=y

# UART
CONFIG_UART_INTERRUPT_DRIVEN=y
CONFIG_UART_LINE_CTRL=n
CONFIG_UART_2_ASYNC=n
CONFIG_UART_ASYNC_API=n
CONFIG_UART_2_NRF_HW_ASYNC=n
CONFIG_NRFX_UARTE2=y

Basic UART code:

void initUart() {
   uart = device_get_binding("UART_2");
	__ASSERT(uart, "Failed to get UART device");
	interrupt_driven(uart);
}

uint16_t writeUARTblock(const uint8_t *buf_block, uint16_t len) {
uint16_t written = 0;

   while (written < len) {
      if (k_fifo_is_empty(&tx_fifo)) {
	      struct tx_uart_data_t *fifo_buf = k_malloc(sizeof(struct tx_uart_data_t));
         if (len - written < UART_BUF_SIZE) {
            fifo_buf->len = len - written;
         } else
            fifo_buf->len = UART_BUF_SIZE;
         memcpy(fifo_buf->data, &buf_block[written], fifo_buf->len);
         written += fifo_buf->len;
	      k_fifo_put(&tx_fifo, fifo_buf);
	      uart_irq_tx_enable(uart);

         k_msleep(BUF_DELAY);
      } else  
         k_msleep(BUF_DELAY);
   }

	return written;
}

Program output:

*** Booting Zephyr OS build v3.1.99-ncs1-1  ***
SerialTest has started
LEDs Enabled HIGH
[00:00:00.488,342] <inf> regulator_fixed: gps-hw-s onoff: 0
[00:00:00.494,689] <inf> regulator_fixed: gps-hw-r onoff: 0
[00:00:00.501,037] <inf> regulator_fixed: gps-pwr-en onoff: 0
[00:00:00.510,070] <inf> lis2dh: lis2dh@18: int1 on [email protected]
[00:00:00.517,059] <inf> lis2dh: lis2dh@18: int2 on [email protected]
[00:00:00.526,428] <inf> lis2dh: fs=2, odr=0x4 lp_en=0x0 scale=9576
*** Booting Zephyr OS build v3.1.99-ncs1-1  ***
SerialTest has started
LEDs Enabled HIGH
[00:00:00.488,677] <inf> regulator_fixed: gps-hw-s onoff: 0
[00:00:00.495,025] <inf> regulator_fixed: gps-hw-r onoff: 0
[00:00:00.501,373] <inf> regulator_fixed: gps-pwr-en onoff: 0
[00:00:00.510,437] <inf> lis2dh: lis2dh@18: int1 on [email protected]
[00:00:00.517,425] <inf> lis2dh: lis2dh@18: int2 on [email protected]
[00:00:00.526,824] <inf> lis2dh: fs=2, odr=0x4 lp_en=0x0 scale=9576
*** Booting Zephyr OS build v3.1.99-ncs1-1  ***
SerialTest has started
LEDs Enabled HIGH