HTML in Incident Description causes Application Error when resolving

We have a custom workflow that creates an incident with a description that contains HTML.  When we try to resolve the incident, we get an Application Error.  We have to remove the HTML from the description and then we can resolve.  So I'm trying to figure out where the problem lies - in the workflow that creates the ticket or in the workflow that resolves it.  The custom workflow uses the "Merge HTML" component.  Why is that component available if it's going to break the process further down the line?