Hi Hari,
When the server stops is doing a controlled stop? in your DMGR SystemOut.log can you see if the server is stopping because a stopManager command?
Take in mind that crontab is for each user, use the next command to review all users crontab
for user in $(cut -f1 -d: /etc/passwd); do crontab -u $user -l; done
Hope this helps. Tell us if you need more support.
regard