Hi,
My guess for 403 works is because it won't hit the following rules. Whereas, ID 112 hit this.
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.+)$ index.php?page=$1 [QSA]
Maybe this cms has a build-in 404 page somewhere, so it redirected...