HTTP 301 returned from registered-email-address/company/{company_number}/eligibility

I’ve been trying to change a test company’s registered email address but I get a 400, bad request whatever I try.

To troubleshoot I thought it would make sense to first check the eligibility of the test company for a registered email address. However, when I make an eligibility request to:
https://api-sandbox.company-information.service.gov.uk/registered-email-address/company/{company_number}/eligibility
I get HTTP 301, moved permanently and ‘/registered-email-address/company/eligibility’ returned in the location header. That URL makes little sense as it does not take the company number anywhere.

Should I get a meaningful response from:
https://api-sandbox.company-information.service.gov.uk/registered-email-address/company/{company_number}/eligibility
Or do I need to use a different URL?
Or is it simply that the eligibility service is not available in the sandbox?

I have passed your query to our development dept for an answer and will update here.

sorry for the delay in responding, but it is still with development, but resource issues are delaying investigation.

Our development team have tried those endpoints in live sandbox and are not able to replicate the error with the information supplied. They also are unable to find a point in the code that would redirect to that URL.
Can we ask if you are still experiencing the issue? if you are, could you supply more details please?