Adalysis automatically monitors all your Final URLs (Ad Final, Mobile Final, Keyword Final, and Ad Extensions URLs) and alerts you when it detects any downtime issues.  It will ping all URLs once a week and display a dashboard warning if any are found:

Step 1

Clicking on the above warning will take you to the below screen showing all the broken URLs

Step 2

You can check the current status of this page to confirm if it is indeed still unreachable:

Step 3

You can view the Ads or keywords that currently use the reported broken URL

If multiple ads use the broken URL, you can edit all these ads with one button click. Select the ads and use the "Edit ads" tool: 

Step 4

Once you fix the broken URL, or correct the Ad/keyword/Ad Extension that use it, you can remove it from the list above and mark the issue as fixed by clicking on the relevant check symbol.