I seem to have found part of the problem. it turned out that I had installed, "wg-installer-server" and it wrote these scripts. I seems wg-client is stable for now.
But I still have the cron job, "Sun Dec 8 18:30:00 2024 cron.err crond[2828]: USER root pid 4112 cmd /usr/share/wginstaller/wg.sh cleanup_wginterfaces"
Don't know where it comes from. Is it possible to delet it from cron job?