There isn't any setting that we manage that would have an effect like this. There are a couple of things to look at. The first is what setting you have for "bburl". This is a standard vBulletin setting and is found under AdminCP >> vBulletin Settings >> Site Name / URL / Contact Details >> Forum URL
This setting should not include forums in the URL.
If it doesn't take a look at the dto_vendor_navbar template and verify it hasn't been modified to use hard URLSs. Each menu entry should use something looking like
PHP Code:
$vboptions[bburl]/dto_vendor.php
with some additional arguments.
If that is correct the last place to look would be your
vBSEO rewrite rules. It may be that "forums" are included in those rewrite rules.
Hopefully one of these options will reveal the issue.
Thanks
Mark