This Google search reveals several things...
  1. You are far from the only person having problems deleting Microsoft Office (Word, Outlook etc.) .TMP or work files
  2. A lot has been written about how to delete these files but no one has found or at least suggested anything resembling a permanent "fix"
  3. The problem has been around since long before Office 2011 and the offending code has apparently been carried over from release to release.
  4. The problem is most likely embedded deep in the Microsoft Office code and a permanent fix will be up to Microsoft and not the user.
Hopefully one or more of those many articles/posts will gave you enough understandable information to enable you to "do it yourself" when the problem recurs and it will recur.

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein