Error while activating BPF: “Invalid Business Process.”

Problem: Today I was not able to activate a business process flow. I got a business process error:

Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=8.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: System.Web.HttpUnhandledException: Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #6D99E8D8Detail: 
<OrganizationServiceFault xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/xrm/2011/Contracts">
  <ActivityId>c0b9f582-977a-49f6-b5ed-2209f1586a05</ActivityId>
  <ErrorCode>-2147220970</ErrorCode>
  <ErrorDetails xmlns:d2p1="http://schemas.datacontract.org/2004/07/System.Collections.Generic" />
  <Message>System.Web.HttpUnhandledException: Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #6D99E8D8</Message>
  <Timestamp>2017-12-11T16:29:45.6122634Z</Timestamp>
  <ExceptionRetriable>false</ExceptionRetriable>
  <ExceptionSource i:nil="true" />
  <InnerFault>
    <ActivityId>c0b9f582-977a-49f6-b5ed-2209f1586a05</ActivityId>
    <ErrorCode>-2147089527</ErrorCode>
    <ErrorDetails xmlns:d3p1="http://schemas.datacontract.org/2004/07/System.Collections.Generic" />
    <Message>Invalid Business Process.</Message>
    <Timestamp>2017-12-11T16:29:45.6122634Z</Timestamp>
    <ExceptionRetriable>false</ExceptionRetriable>
    <ExceptionSource i:nil="true" />
    <InnerFault i:nil="true" />
    <OriginalException i:nil="true" />
    <TraceText i:nil="true" />
  </InnerFault>
  <OriginalException i:nil="true" />
  <TraceText i:nil="true" />
</OrganizationServiceFault>

Solution: After some research I found the problem. There was a related Process which was in draft modus. After activating the process I was able to activate the BPF.

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