Why do I have to re-select the same fitment information to make it valid?

Although this seems repetitive, when the VCdb is updated, the "ID" corresponding to certain fitment information will sometimes be changed.

These changes may be in other fields which relate to the vehicle information you're needing to re-select, but may not be visible with your selection, but the overall ID number has been changed.

So it may seem you are re-selecting, but you are updating the VCdb ID associated to your fitment.