Navigation Issue causes a 404 error

@property

I'm trying to resolve a navigation issue that causes users to see a 404-error every time they try to reach a particular section of our website. The site was built by our consultants who are long since gone.

We're running Mont Blanc.

The code from the SC.Configuration.js file looks like this:

{
            text: _('Products').translate()
        ,    href: '/'
        ,    'class': 'header-menu-level1-anchor'
            // @property {Array<NavigationData>} categories
        ,    categories: [
                {
                    text: _('BMX').translate()
                ,    href: '/custitem_itemcat_main/BMX'
                ,    'class': 'header-menu-level2-anchor'
                ,    categories: navigationBMXCategories
                }
            ,    {
                    text: _('MTB').translate()
                ,    href: '/custitem_itemcat_main/MTB'
                ,    'class': 'header-menu-level2-anchor'
                ,    categories: navigationMTBCategories
                }
            ,   {
                    text: _('SALE').translate()