What is "destinationURL" actually tracking?? This is a custom dimensions...
I am willing to bet there is no issue here at all... since eVars when they aren't set with any value will report "unspecified". This is completely expected.
I am going to assume, based on the name, that "Destination URL" is tracking the URL that is clicked from specific links on the page (where the user is going)... this means that every page view, click, action, etc up until those links are clicked will result in "unspecified".
This is normal and expected behaviour, and in your case, all you need to do is hide unspecified in your freeform table because it doesn't add any context to this particular report....