Problems were detected with this header / 301 redirects to 403

Hello,

Redirection plugin is giving me a 403 status when I redirect a recently removed url to my home page. Error message: “Problems were detected with this header
Duplicate header. There is another header with this name and this may cause problems.” Any idea what this warning means?

Redirects that I send to a url with a related path gives me a 200. Am I missing something? The redirect works on Google, but not within Redirection: https://redirect.li/http/?url=https%3A%2F%2Fevercleantn.com%2Fthe-science-of-carpet-cleaning%2F

Thank you

The page I need help with: [log in to see the link]