Change Organization ID - Broken?

When I change the external org ID for an organization from one in-use (1925) to another that is not-in-use (9843), the process completes  successfully and the org ID is updated to 9843. However, if I try to create a new external organization using the no-longer-in-use ID (1925), I get a a data conflict message:

Data being added conflicts with existing data. (18,2)

When adding a new item to the database, the system found a conflicting item already exists.

This problem can happen if another user has entered similar information at the same time as you.  Note the changes you have made, cancel the page, then retry your changes.