Other things that could trigger duplicate page titles and meta descriptions -
These links all have the same page titles, AND they will trigger short titles/descriptions/tags:
https://www.ubbdev.com/forums/ubbthreads.php/forums/1/1/https://www.ubbdev.com/forums/ubbthreads.php/forums/1/2/https://www.ubbdev.com/forums/ubbthreads.php/forums/1/3/https://www.ubbdev.com/forums/ubbthreads.php/forums/1/4/These are Page 1,2,3,4 of the "Announcements" forum.
As a side note, Stock UBBT 7.5.8 does not come with a "description" line in the header.tpl file.
Common items in 2014 that stock UBBT 7.5.8 does not come with:
meta name="robots"
meta id="viewport"
meta name="keywords"
meta name="description"
For a few years now, Google has said that they dont use meta keywords for ranking.
Its not necessary to set a viewport on UBBT since its not optimized for mobile, out of the box. But setting one should be done, so your text doesnt get "font boosted" incorrectly by Mobile Chrome.
Robots? Do you want your stuff cached or archived in different engines? this would be one of the place where you could tell the spiders what you want done.