[Koha] Koha zebra indexing stops every day morning.

Hello, I am using Koha 16.05.04.000 version on Ubuntu 16.04.1 LTS. Problem is that, each day morning OPAC searching stops. We checked the status of Koha-common service. Its active. But after restarting koha-common, everything starts working fine. Checked koha logs files for any errors. But no errors logged in log files. I am not able to understand from where do I start to troubleshoot the problem. Kindly help me to resolve this problem. Thanks & Regards, Sandeep Ulhalkar