There has been an occasion where an error was occurring within the logs and mentions only the GUID of the model in the error and therefore there is no way of telling what model is causing the issue from the log.
The error log will be referencing which workflow project this error is in. With this information, navigate to the workflow install directory:
C:\Program Files\Symantec\Workflow\WorkflowProjects\{Applicaiton Name}
Take a copy of the Primary.model file and place this on the desktop of the server. Right click this file and change the file extension from .model to .zip
You should then be able to open the zipped file and a list of 6/7 files should be showing within the primary.zip file.
Open the IStorableObject.xml file and using the GUID from error log you can conduct a search using the model GUID to find the model name, which will then allow you to now diagnose the issue within the workflow.
Alex will be releasing an article in the next few weeks which allows all of this functionality and information to be viewed from a custom plugin available in any workflow project. More information on other workflow plugins he has written can be found here: https://www.symantec.com/connect/articles/workflow-plugins. Check them out!