Issue:
For the third time in as many weeks, I have had this weird problem in updating the Workflow Settings for one of the SharePoint Lists workflows, whenever I change the Start Options to “Start workflow automatically when an item is created/changed” and publish it to SharePoint, the start behavior of the WF execution doesn’t change and once I refresh the SharePoint Designer (SPD) and check the start options again, it returns as it was “Allow this workflow to be manually started”.
Cause:
After many hours of fighting with SPD, I went to a conclusion that SPD will cause this issue sometimes because of certain Workflow Activities .NET assemblies caching problem within the SPD.
Resolution:
The solution? It’s simple, you have to clear the SPD Workflow Activities Assembly Cache Folders:
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Close the SharePoint Designer.
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Open the Windows Application Data Store Folder by going to Start->Run and then type %APPDATA%\Roaming\Microsoft\SharePoint Designer\ProxyAssemblyCache (%APPDATA% is a Windows Environment Variable that points to the Windows Applications Store Folders) and press Enter.
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Delete all these directories inside the ProxyAssemblyCache Folder.
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Browse again to %LOCALAPPDATA%\Microsoft\Windows\Temporary Internet Files\WebTempDir
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Delete all the files inside this Folder.
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Run SPD again, and everything will work out fine
Posted by mohkanaan 
