Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32f1/STM32F107/UART4/SR#0x0
UART4 SR
Parity error
Framing error
Noise error flag
Overrun error
IDLE line detected
Read data register not empty
Transmission complete
Transmit data register empty
LIN break detection flag
https://github.com/modm-io/cmsis-svd-stm32