Content Index status of all or most of the mailbox databases in the environment shows "Unknown"

I have posted a question on Microsoft technet forum related to the following question. I would appreciate some help

Question Link:
https://social.technet.microsoft.com/Forums/exchange/en-US/e17cbbda-2973-4c6d-9264-823f9d4a1968/content-index-status-of-all-or-most-of-the-mailbox-databases-in-the-environment-shows-unknown?forum=exchangesvradmin

My story:
I have installed Exchange 2013 CU8 on Windows 2012 in coexistence with Exchange 2007 SP3 Rollup 16 and as soon as I installed the MBX roles (2 servers) the default databases came with Unknown index state.

I have followed this article https://support.microsoft.com/en-us/kb/2807668 and restarted the servers which brought the DB to healthy again but after couple of minutes it fails once again.

Is this a bug on Exchange 2013 CU8 with Windows 2012? Because I already installed it on 2012 R2 and I didn't have this issue.

I would really appreciate any help as I don't want to reinstall Exchange again.
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Mohammed HamadaSenior IT ConsultantAsked:
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Mohammed HamadaSenior IT ConsultantAuthor Commented:
Not Solved, I ended up by rebuilding Mailbox servers and I still don't know what's the cause of this failure for the mailbox servers after new installation.

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Mohammed HamadaSenior IT ConsultantAuthor Commented:
Solved by reinstalling Mailbox servers
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