UBB.threads PHP Forum Software Community Forums UBB.threads 7 Version 7 Support Error on backup inside the forum

If I try to use the option to backup from inside the forum:
Tools & Info -->Database Tools --> Backup Tables -->
and hit the (Click to test directory.) I'm getting this error:
Fatal error: Call to undefined function smartyPrepare() in /home/My_USER/public_html/forum/libs/html.inc.php on line 695

The folder I have there for backup is:
/home/My_USER/public_html/forum/admin/backup/
and it's 0744 permissions.

Version of Forum is 7.5.9
PHP Version 5.6.27

Could not find any mention to this error here.