I’m getting the same, long error list on my validation report.
example:
Mailman : Apache redirect for /cgi-bin/mailman goes to https://domain.com:443/virtualmin-mailman/unauthenticated/$1.cgihttps://domain.com:10001 instead of the correct Virtualmin URL under https://domain.com:10001
so I logged into the webmin’s Apache Web server module, and under the appropriate Virtual Server, found the “Regexp URL redirect” (cgi-bin/mailman …etc) …
I know this is 5 years old, but just in case anyone is stumbling on this, all I had to do was correct the port number. I had changed the default port of Webmin from 10000 to something else, but the Mailman Redirects settings did not get updated, so to fix, I just changed the port number in the url https://domain.com:10000/virtualmin-mailman/unauthenticated/$1.cgi$3 (I left the rest untouched) and then validation succeeded.