Document Locked Error in Workflow

What is a good standard with dealing with locked documents during a workflow? Here is the scenario:

User has a task assigned and opens the document twice (by mistake). On the second screen the user puts the task stamp and closes the document. This task does not attempt to edit the doucument. The next step will edit the index entries, but fails because the user still has the document locked from the first screen. 

I'm curious to hear the answer to this, too.  I have this problem on a regular basis because a lot of DW users at one facility have the viewer setup to open the document always in a separate viewer window (with index dialog, I believe) so they don't even accidentally open two copies of the document to do their task, just one, which locks the document and causes the workflow to fail after their task if they forget to close the document (which they do, regularly, because human).

The best Idea I have come up so far has been to catch the error and send it back to the previous task. Send an email to the user with the error message. Put a wait and after X time attempt to write again. But then again it would be complicated because I would have to have a condition to only send the error in case of the lockdown specific error, and I am not sure how to do that.