Garbled Characters in HAL_UART_Transmit_IT on STM32 F303RE Causes and Solutions

I’m using

HAL_UART_Transmit_IT

HAL_UART_Transmit_IT

in two places with the Nucleo F303RE board. In

HAL_UART_RxCpltCallback

HAL_UART_RxCpltCallback

, I use it to echo received UART data, and it works fine.
In

Print_CAN_Frame

Print_CAN_Frame

, I send messages every 3 seconds. Previously, I used

HAL_UART_Transmit

HAL_UART_Transmit

, which worked, but after switching to

HAL_UART_Transmit_IT

HAL_UART_Transmit_IT

, I get garbled characters in TeraTerm. Both functions use the same UART configuration: BaudRate 115200, WordLength 8B, StopBits 1, Parity None, TX/RX Mode.
The issue appears only with interrupt-driven transmission. What could be causing this behavior, considering both functions take identical arguments, and how should I handle potential buffer or timing issues?

Here is my code file;