By default the two should both be 3.3V. However, there is a level shift jumper (I have never used it before) which I think can change it to 1.8V. Is it possible one side has the jumper such that it is 1.8V?
One other question is if the output of “$LANG” is the same at both sides where the serial console program and generated data are run. If for some reason the character set differs, then the data would be 100% correct, but displayed wrong.
The supported mode is to get UART log through a host PC. Would need to check with our teams if we can support getting the log from the other Jetson device in the future.
If you have to run this use-case, please try linuxdev’s suggestion.