This is a usability problem.

In VID, when attempting to Add VF-Module, if the operation is not successful, the attempted VF-Module does not show on the VID screen, although it was partially created and needs to be deleted. So when the user tries a second time to Add VF-Module with the same values as they entered the first time, it will fail but the user doesn't know why because the first attempt is not shown on the screen.

Instead of trying again, the user has to Refresh the VID screen to see the partially created VF-Module, Delete it, make whatever changes are needed, and then re-try the Add VF-Module.

This problem seems to have been introduced in Casablanca.