What to run
Use Redirect Checker. The result is from Cloudflare.
How to read the result
A repeated URL in the hop list, or a stopped reason of loop, is the loop.
Compare path, trailing slash, and http/https on the repeated pair.
What to open next
Open htaccess Redirect Generator to draft a single correcting rule. That tool stays in the browser.
Do not stack a new rule on the old one without re-checking.