As the item no longer is listed in the Item 2 box of the results tab, Navisworks is no longer able to identify that item as still being in the model. If the item was moved or hidden, it would still be listed in the Item 2 window. Since Navisworks no longer can find that item to determine it is clashing with Item 2, the result is resolved.
This can occur for a number of reasons:
1. The item was actually deleted from the model an no longer exists 2. The item was modified by deleting or replacing it in such a way that its GUID has changed. 3. The Entire CAD model that was deleted and appended back in. 4. The GUIDs of the elements in the entire model have changed. This occurs for example if you export to an AutoCAD DWG from Revit as each time you export, the GUIDs are different regardless of what you’ve changed in Revit.
In Items 2-4 above, as another item resides in the same place, a new clash result is generated that corresponds to the resolved. Do you still have the previous version of the Model that was updated? If so, if you temporarily swap out the updated model with it to re-run the clash tests, the item will likely be listed again and you can check what that item is and if there is an item in that same location in the updated version.
John Lipp Support Specialist Product Support Autodesk, Inc.