I have some posts that had URLs pointing to other threads done when using classic version.
Now upgraded to V7.2 and if clicking on the url in a post instead of going to the post URL directed it takes user to the portal page.

URL of course in part had UBB directory which I have not deleted UBB classic but also has the redirector when upgrade was done.

An fix or work around ?

Well, if it's redirecting to a THREAD it should auto match using the redirectors; if it's trying to redirect from a FORUM it'll redirect to the main page only