After reading this post and having already upgraded to v4.0.3, I ran a test to see if that "condition" was also present on my system (DP 800 10.3.4).
When I attempted to import a "duplicate", the normal dialog box appeared asking if I wanted to import the duplicate. All was as His Steveness divines and thus I was unable to repeat the problem.
I do recall that when I first installed v4.0.3, Repairing Permissions was quite extensive (routine since then). So maybe Repairing Permissions and rePrebinding is called for.
Sorry my feedback is not too helpful.