Ungroup elements in document - Revit - Dynamo
Ungrouping is an action that requires a transaction in the Revit API (which, in turn, needs a document reference). The Ungroup node uses the current document for that. For it to work on other documents in the background, you would have to pass the respective model‘s doc reference. I am writing this from my phone so I can‘t be more exact than this but you could look at some of Clockwork‘s selection nodes (that have optional doc inputs) on how to modify the node to better suit your needs.