MSP430G2553: I2C issues when not connected to PC

I am experiencing issues using I2C on a msp430g2553 on a PCB. When I flash my code onto the external board by connecting via the ezFET side of the launchpad, I experience no issues (even when loading rather than going into debug mode on CCS). However, after flashing my code and disconnecting from the launchpad, my program gets stuck in my InitMPU() function. The initMPU() function simply transmits data using the TransmitByte() function in i2c.c (see below). 

 Here is my i2c.c file, where initI2C() and TransmitByte() are called from main.

/*
 * i2c.c
 *
 *  Created on: 4 Apr 2024
 *      Author: Chris
 */

#include "i2c.h"

// Function to config I2C regs - 400 kHz operating freq
void initI2C(void) {

    P1SEL |= SCL + SDA;                         // Config P1.6 SCL and 1.7 SDA
    P1SEL2 |= SCL + SDA;
    UCB0CTL1 |= UCSWRST;                        // Enable SW reset - known state
    UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC;       // Make MCU master & put in synchronous mode
    UCB0CTL1 = UCSSEL_2 + UCSWRST;              // SMCLK approx 1 MHz
    UCB0BR0 = 9;                                // /3 to get fast rate approx 400 kHz
    UCB0BR1 = 1;
    UCB0I2CSA = MPU_SLAVE_ADDRESS;              // Set slave address of mpu6050
    UCB0CTL1 &= ~UCSWRST;                       // Exit SW reset now that registers are configured
}

int IsI2CBusy(){
        if(UCB0STAT & UCBBUSY){
            return 1;                           // BUS BUSY
        } else{
            return 0;                           // BUS NOT BUSY
        }
}

// Function to read a single byte of given I2C Slave Address
char ReceiveByte(char register_address){

    volatile char byte;
    while (UCB0CTL1 & UCTXSTP);                 // Wait for our prev stop condition to be sent (just in case..)
    UCB0CTL1 |= UCTR + UCTXSTT;                 // Lets start in transmit MODE
    while((IFG2 & UCB0TXIFG) == 0);             // Wait for MPU66050 Device Address to be sent
    UCB0TXBUF = register_address;               // After we get ACK, lets send register address we want to read
    while((IFG2 & UCB0TXIFG) == 0);             // Wait for ACK...
    UCB0CTL1 &= ~UCTR ;                         // Now we can receive data from the register address
    UCB0CTL1 |= UCTXSTT + UCTXNACK;             // Send START and we respond with NACK for single byte read
    while (UCB0CTL1 & UCTXSTT);                 // Wait for start to complete...
    UCB0CTL1 |= UCTXSTP;                        // Send stop
    while(!(IFG2 & UCB0RXIFG));                 // Wait until we receive
    byte = UCB0RXBUF;                           // Read the byte
    return byte;

}

void TransmitByte(char register_address, char data){

    while (UCB0CTL1 & UCTXSTP);                 // Wait for our prev stop condition to be sent (just in case..)
    UCB0CTL1 |= UCTR + UCTXSTT;                 //
    while((IFG2 & UCB0TXIFG) == 0);             // Wait for MPU66050 Device Address to be sent
    UCB0TXBUF = register_address;               // After we get ACK, lets send register address we want to read
    while((IFG2 & UCB0TXIFG) == 0);             // Wait until our reg address is sent
    UCB0TXBUF = data;                           // Now we can send our data to that address
    while((IFG2 & UCB0TXIFG) == 0);             // Wait...
    UCB0CTL1 |= UCTXSTP;                        // STOP
    IFG2 &= ~UCB0TXIFG;                         // Clear Flag

}

And below is my main (a shortened version). Again, InitMPU() simply calls TransmitByte() from i2c.c. When I don't call InitMPU(), the code works as expected when the board is powered externally and not connected to the launchpad. When I call InitMPU(), the program must be getting stuck in a while loop present in TransmitByte(). I'm at a loss for why this might be the case when not connected to the ezFET side of the launchpad as it works when connected  with no issues.

int main(void)
{
    WDTCTL = WDTPW | WDTHOLD;                               // stop watchdog timer
    __enable_interrupt();


    IFG2 = 0x00;                                           // Reset IFG2
    initI2C();                                             // Init I2C for reading mpu6050
    while ( IsI2CBusy() );

    initMPU();  
}