BOS Model Error: DataColumnMapping.SourceColumn is required to be unique

   We are having a intermittent but persistent error occurring with the 
Model for the project I've been working on. When the problem occurs when
 trying to login to the persistence manager. And it returns the error:

The DataColumnMapping.SourceColumn is required to be unique. 'Inactive' already exists in the collection.

This error is a little strange because the column 'Inactive' has been present in the database since it was created, and has not been modified since. This error will occasionally occur when I need to update the Model (which I make sure to do a mandatory update to our program so all users have a current version on the Model to work from). But the error will also occasionally occur days after I've made the update to the Model. 

To clear the error and get the Model working again, I'm forced to make another update to the Model. Doing a recompile of the Model (even when clearing the build destination folder) doesn't clear the error, I have to change something in the Model and update the server before the error will be cleared. 

I've been trying to figure out what could be causing this problem to occur but so far have made little progress beyond handling the symptoms of the problem (namely the ones that the end-user would see). Any help that could be provided would be appreciated.