I have a system that contains 4 workflows to manage content and the approval process.  The first two workflow is triggered by "Run on New" and the second and third workflow runs by a Start Workflow commands in sequence from the previous workflow.  The third workflow also runs on modify (with an exception for a field that is not changed in this scenario).  The fourth workflow runs as needed when called by the third workflow.  

My issue is the third (main) workflow is starting to run as the second workflow is starting.  I assume it is being started by the change to the list made by Workflow 1.  This change being done by the workflow should not be a change that should cause the workflow to run.  This causes the "scheduled" run of the workflow to cause an exception and terminate since an instance of the workflow is already in progress.

Has anyone seen where a workflow started by another workflow sporadically starts when it is not expected to start?  A simple diagram is attached below to show the structure.