Logon Failure Active Directory

[D Nik]

Hello

I have the Problem with the logon on Active Directory.
The Bonobo Git Server and the Git Service works fine but the IIS and th DC log again and again logon failures.
DC say:

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Kerberos pre-authentication failed.

Account Information:
    Security ID:        domain\user
    Account Name:        user

Service Information:
    Service Name:        krbtgt/domain

Network Information:
    Client Address:        ::ffff:172.16.31.54   <- this is the Bonobo Git Server
    Client Port:        49296

Additional Information:
    Ticket Options:        0x40810010
    Failure Code:        0x18
    Pre-Authentication Type:    2

Certificate Information:
    Certificate Issuer Name:       
    Certificate Serial Number:    
    Certificate Thumbprint:       

Certificate information is only provided if a certificate was used for pre-authentication.

Pre-authentication types, ticket options and failure codes are defined in RFC 4120.

If the ticket was malformed or damaged during transit and could not be decrypted, then many fields in this event might not be present.
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you have a idea?

thank you
nik