How to handle the case of a new release having the same UPC and disk ID of a previous one? 

This is the case of the DVD "The Dam Busters" (The Essential War Collection) that I own:

it has the same UPC/disk ID of your entry recorded with disk id=8C8E0E47CE2109A7 , released in 2002;

but mine is a different release, published in 2005: it correspond to the dvd profile available here in the Allmovie website, and with the following cover:

At the moment, you can only make changes locally, but not contribute the new details (except Disc ID, but that is the same in this case). The system only allows one entry per combintation of UPC/EAN and locality, and the rules prescribe that the first release is to be maintained.

I am not quite sure if the rules allow to contribute the new release using the Disc ID as identifier  rather than the UPC/EAN.

Quoting No_Name_Needed:

Quote:
At least it's the same movie for you. When I got the new release The Being / Cop Killers last week the UPC was the same than a Fred Williamson's movie released by this label last year...

I've seen a few of those and it is annoying. But at least the disc IDs will be different and the later contribution can be made using the disc ID as identifier.