assign output of command to variable in bash script run by root cron - linux

Question

I have been trying to write a script that will backup my minecraft server but only run if I am not actively on the server. The way i am trying to do this is by parsing the output of top and grepping the process name and getting the CPU usage. When I am not on the server the usage is usually less than 10. The server is run as a service so in order to bring it down before the backup and to bring it back up I need to use systemctl stop and systemctl start in so it need to be run as root. This is the script I have:
#!/bin/bash
PATH="$PATH:/usr/bin:/bin"
CPU=`/usr/bin/top -b n1 | /usr/bin/grep bedrock_server | /usr/bin/awk '{ print $9 }' | /usr/bin/cut -d . -f 1`
DATE=`date '+\%m-\%d'`
dirname="/home/brandon/bedrock-backups/$DATE"
if [ "$CPU" -lt 20 ];
then
systemctl stop bedrock-server.service && \
mkdir -p $dirname && chown brandon $dirname && chmod 777 $dirname && \
cd /home/brandon && \
tar -czf $dirname/bedrock-backup.tar bedrock/ && \
chown brandon $dirname/bedrock-backup.tar && chmod 777 $dirname/bedrock-backup.tar && \
echo "Backup Completed Successfully" && \
systemctl start bedrock-server.service
else
echo "Backup terminated due to server activity" && \
exit
fi
The issue seems to be that the output of the top command and all the subsequent parsing does not get assigned to CPU so the script errors out at if [ "$CPU" -lt 20 ] with the error integer expression expected. I tried to run the script in cron's env by adding the line env > ~/cronenv to root's crontab and have it run once then use env - `cat ~/cronenv` /bin/sh to get into crons environment. I run
CPU=`top -b n1 | grep bedrock_server | awk '{ print $9 }' | cut -d . -f 1`
and it works. I tried again as a cron job and I get the same error. Then I read that full paths to commands should be used inside cron so I added /usr/bin to the commands as seen above.
I've tried using #!/bin/sh as well as #!/bin/bash for the shebang. The crontab entry is as follows :
# m h dom mon dow command
SHELL=/bin/bash
PATH="$PATH:/usr/bin:/bin"
27 22 * * * /bin/bash /home/brandon/bin/scripts/backup-bedrock
#* * * * * env > ~/cronenv
I can even run the full script in the cronenv but not scheduled as a cron job.
I do not know what else to try or what I am doing wrong, hoping someone can help me.
Thanks!
Also this is on Ubuntu 20.04 if that matters