Umount device busy after reboot it mounts

I ve a playbook which is trying to umount

#umount -a -t nfs4

When this line executes it is throwing
Unmount.nfs4: /firewalker: device busy

I checked there is no entry in /etc/fstab for firewalker. But I found one entry in crontab

42 1 * * * /usr/local/bin/firewalker.wrapper LINUX > /dev/null 2>&1

JFYI In the playbook before it executes impunity command it restarts the machine.

I found one entry

# ll /etc/rc.d/rc*/*firewalker
lrwxrwxrwx 1 root root 22 12月  7  2022 /etc/rc.d/rc2.d/S99firewalker -> /etc/init.d/firewalker
lrwxrwxrwx 1 root root 22 12月  7  2022 /etc/rc.d/rc3.d/S99firewalker -> /etc/init.d/firewalker

Please suggest how to debug and proceed this.

Thanks in advance