Garbled Characters in HAL_UART_Transmit_IT on STM32 F303RE Causes and Solutions

I’m using HAL_UART_Transmit_IT in two places with the Nucleo F303RE board. In HAL_UART_RxCpltCallback, I use it to echo received UART data, and it works fine. In Print_CAN_Frame, I send messages every 3 seconds. Previously, I used HAL_UART_Transmit, which worked, but after switching to 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;