Exchange 2013 - Search Index corrupted, cannot be fixed.

Hi all,

We have an Exchange 2013 server of which the search index is corrupted.
The message when checking the search index in Powershell is as following:

Get-MailboxDatabaseCopyStatus -Server SERVERNAME | FL Name, *Index*

Name : Mailbox Database 1
ContentIndexState : FailedAndSuspendedContent
IndexErrorMessage : The content index is corrupted.
ContentIndexErrorCode : 19

When checking the Event viewer, we see the following message logged:

Log Name:      Application
Source:        MSExchangeFastSearch
Date:          23-4-2015 8:57:07
Event ID:      1009
Task Category: General
Level:         Warning
Keywords:      Classic
User:          N/A
Computer:      MAILSERVER

Description:The indexing of mailbox database Mailbox Database 1 encountered an unexpected exception.

Error details: Microsoft.Exchange.Search.Core.Abstraction.OperationFailedException: The component operation has failed.
--->Microsoft.Exchange.Search.Engine.FeedingSkippedForCorruptionException: "Feeding was skipped for '412595f4-98d0-4bf6-8ac2-89457c37b872 (Mailbox Database 1)' due to the state 'Failed', error code: 'CatalogCorruption', failure code: '4036033', failure reason: '5 consecutive merges failed. Requesting seeding as it is >= 5.'."  
at Microsoft.Exchange.Search.Engine.SearchFeedingController.InternalExecutionStart()   at Microsoft.Exchange.Search.Core.Common.Executable.InternalExecutionStart(Object state)   --- End of inner exception stack trace ---   at Microsoft.Exchange.Search.Core.Common.Executable.EndExecute(IAsyncResult asyncResult)  
at Microsoft.Exchange.Search.Engine.SearchRootController.ExecuteComplete(IAsyncResult asyncResult)

In this message, the problem seems to be in the following line:

"Feeding was skipped for '412595f4-98d0-4bf6-8ac2-89457c37b872 (Mailbox Database 1)'
due to the state 'Failed', error code: 'CatalogCorruption',
failure code: '4036033', failure reason: '5 consecutive merges failed. Requesting seeding as it is >= 5

I just can't find the solution for it. What i've tried:

- Upgrade Exchange 2013 to CU8.
- Stopped the search services, deleted the search index folder and started the services. This triggers the re-creation of the search index, but after some hours indexing, it fails again with the same reason.
- Executed a RepairMailboxRequest to check all mailboxes on the mailserver for problems, this came up with no problems.

Anyone know how I can solve this issue?