How do I handle a redirect chain issue pertaining to a page that doesn't actually exist on my site?

[NiteSkirm]

I have a page showing up on the insights report as being a redirect chain. This page however does not exist as far as I can tell. It is not on my dashboard anywhere and pointing a browser to it produces a messy page with Wordpress theme error code spit out.  How do I track this down to clean it up if the page does not exist within my Wordpress installation? The page for reference is https://butlermobility.com/dealers/downloads. As it stands today the dealers and downloads pages are separate. There is no downloads sub page within the dealers section.

[paints-n-design]

Its a redirect from non trailing-slash to trailing-slash version of the page, which ends up in a broken 404-Page.

Remove all internal Links to the Dealers/Downloads page. That should solve the Problems from an SEO POV. But why the 404-Page is broken? Think it is  the breadcrumb, shouldn't came up if all linked Pages exist. Funny is - I don't saw breadcrumbs anywhere.

BTW - on my Laptop it is impossible to use the menu.  The basket Icon is in the second line of your menu, makes it impossible to click on a sub-link in the menu.

[NiteSkirm]

Thank you so much for the response. I have addressed the layout problem (Wordpress themes give me headaches sometimes). I will look into tracking down the internal links next.