Did you know that there are 25 known issues with Procurement-related invalid objects after migrating to R12? Check out Doc ID 1527251.1'Guide to R12 Invalids for Procurement Products'.
The note provides the steps to first attempt to compile them through adadmin then, for any remaining invalids, the note gives instructions for known fixes. So check out the note now if you have invalid Procurement objects after upgrading to R12, or if you are in the process of upgrading, check the recommended patches and avoid potential problems from happening.