The %20 blank space is ok and not triggering the 403 error. I believe the round bracket code characters/parenthesis around “Camaro” are what is triggering the 403 error: (Camaro)
Is UBB Forum installed outside of your WordPress site? Is it installed in its own folder as a 3rd party application?
Example:
UBB Forum is installed in this folder: /public_html/forums/ and your WordPress site is installed either in the root of the site or in a subfolder: /public_html/wordpress folders are here: wp-admin, wp-includes, etc…. or WordPress is installed in a subfolder: /public_html/wordpress-site/wordpress folders are here: wp-admin, wp-includes, etc…