There are 2 places to set-up click-throughs,  Editor  Deployments and then on the Preview Page you can test and check though Click-throughs by selecting different items.
- Click-throughs can either be set-up via an Element's " ELEMENTS Call-to-Action" (Diagram A.)
- Overall Click-through for the entire Creative (Diagram B.)
A. Element Settings - Elements Call-to-Action B. Creative Settings- Set up Click-Through
 Deployments (Summary Page)
- When you set-up a Deployment to get an ad tag, you have the ability to Edit or Set-up a Click-through URL. You can do this by "Edit Deployment"
- When Editing a Deployment it will overwrite what your set-up in the editor. This makes for a good way to templatize creatives by having a placeholder URL for many different elements or the creative and then when you get your ad tag, you can change the URL for that deployment.
So to answer this Question?
We have a partner that had duplicated and used a creative as a template, so the older URLS that had been set-up in the editor were used. They overwrote them using deployments, but on the preview page, they were still getting the old click-throughs.