I was seeing this error when trying to check in a document after completing the required metadata in Word (via DIP). I found this post claiming the issue was due to the content type of the document containing a managed metadata field. Although that sounded far fetched, I ended up following the workaround instructions and adding a new managed metadata field directly to my library (Test with one term- test). I then deleted the field, and suddenly I could check my document in! Weird.
I also saw this error when I used the Specify default content feature of Document Sets – automatically creating a number of documents from templates, within a new set. I could not complete the metadata and check those documents in. When I turned off check in/out on the library, I could no longer get to the DIP properties in Word. The only way to set the document metadata was to use the edit form in SharePoint. I never got around this issue. If anyone has an ideas, please let me know.