An issue that I ran across the other day using Inventor 2017 was my part file was acting like it was locked. This issue was not allowing me to edit or delete any features or sketches in my part file. In addition, only a couple of the commands in my ribbon were available and everything else was grayed out. Come to find out this has been an issue since Inventor 2015 and is currently being investigated by Autodesk for a possible cause and resolution. The good news is that there is a workaround which is shown below.
Issue: Features and Sketches unavailable
1.) Close all documents.
2.) Invoke the VBA Editor.
3.) Within the editor under Application Project (Module1) add the following script.
Dim oDoc As Document
Set oDoc = ThisApplication.ActiveDocument
oDoc.DisabledCommandTypes = 0
4.) Do not close the VBA Editor. Return back to the Inventor user interface and open the document that is locked. Once the document is open go back to the VBA Editor and run the script that was pasted into Module1.
After running the script the file should now be unlocked and everything back to normal as shown below.