While investigating Salesforce importer problems, we uncovered a bug in setting properties contributed through extensions. Basically, if you create an extension model adding properties to a Table, for instance, when you actually extend a model and set the properties the model is NOT changed.
1) create extension model extending a relational table
2) add this extension model to a relational model
3) Open the relational model in editor
4) Select a relational table in explorer
5) Change an extended property value
6) Editor should now be "Dirty" (i.e. requires save) but it's not
Note that we did upgrade EMF from version 2.1 to 2.4 for Teiid Designer, so that's a place to start.