Bash script with pipe can not working as expceted in crontab

start.sh

PID=`ps -ef | grep 'anticheat' | grep -v 'grep' | awk '{print $2;}'`
if [ ! -z "$PID" ]; then
    echo "PID FOUNDED :" $PID
    echo "IF YOU WANNA TO RESTART, PLEASE USE THE RESTART SCRIPT"
    exit
else
    # start service
    if [ -z "$PID" ]; then
        echo "START SERVER ERROR"
        exit
    else
        echo "START SERVER SUCCESSFULLY"
    fi
fi

output for commend line

++ pwd
+ cur_dir=/search/odin/online/anticheat
+ anticheat_bin=anticheat
++ ps -ef
++ grep anticheat
++ grep -v grep
++ awk '{print $2;}'
+ PID=17821
+ '[' '!' -z 17821 ']'
+ echo 'PID FOUNDED :' 17821
PID FOUNDED : 17821
+ echo 'IF YOU WANNA TO RESTART, PLEASE USE THE RESTART SCRIPT'
IF YOU WANNA TO RESTART, PLEASE USE THE RESTART SCRIPT
+ exit

it can work rightly when I run a bash shell in commend line, however it doesn't work as expected in crontab.

++ grep anticheat
++ grep -v grep
++ ps -ef
++ awk -F ' ' '{print $2}'
+ PID='17821
23184'

how can I fix it?