openlitespeed server restarting every minute and sent me error email

guys I’m having problem every 1 minute openlitespeed from my server restarts and sends me an email “error fix 503” and I have already debuted this option on openlitespeed itself, the system I am using is Centos 7 and in /usr/local/lsws/logs/stderr.log this appears exactly every 1 minute too:

sh: usermod: command not found
sh: usermod: command not found
sh: usermod: command not found
sh: usermod: command not found
sh: usermod: command not found