UART not send data

Hi, i have a problem with the ttyS4 port in VIM1 (VIM1_Ubuntu-xfce-focal_Linux-4.9_arm64_EMMC_V1.0.7-211118-develop.img). The port receives the correct message, but not send data.
i have configured /boot/env.txt with overlays=uart4
im using a python script with pyserial library (working with USB-serial converter, 9600baud).
I observed that when i send a large message from VIM to another serial-usb converter, trash is received.
Any idea about the problem? Do you need another information?

@jack.zhao Jack, Please help to check this issue.

@chona_diaz Hi,I used the serial port tool to test the serial port ttyS4 data sending and receiving of VIM1 board. It is normal. There is no problem you said. The baud rate I set is 115200. Please check your operation carefully