Have latest regular version from GitHub running in Docker on unRAID, not sure how long it has been happening, but only had someone complain recently that when viewing their payments through email link, they get this error. I can reproduce myself, no only link such as for invoice gives them problem and they can use that to navigate to payments section and view any payment just fine.
This is error line from log.
127.0.0.1 - 07/Mar/2022:17:01:40 +0000 “GET /index.php” 404
When you say Base URL, is that the same thing as the APP_URL in the Docker settings and/or the Domain URL in the Client Portal Settings? Both are same thing, invoiceninja.mydomain.com