After enabling "monitor security flow", clearing the log file once the monitor security flow has been stopped after it is started, the "show log <file-name>" displays unreadable format in the output.

root@SRX> show log traffic
Aug 21 11:16:51 13:27:58.*********:?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????

Issue isolation:

- Run the command below
monitor security flow start
- Generate traffic and run the below command again
monitor security flow stop
- Clear the log entry using the below command
clear log <file-name>
monitor security flow start
- Generate traffic
monitor security flow stop
show log <file-name>

This is addressed and resolved in the JUNOS releases:- junos:21.4R3-S9 junos:22.4R3-S5