This website is awesome, dont change. Often with these things the idea is good but people won't want to do the hard work.

I had a quick look and there may be some copies of the forum. For example,
https://web.archive.org/web/20060101000000*/microwaves101.com

This is from 2006
https://web.archive.org/web/20060323115001/http://www.microwaves101.com/cgi-bin/yabb/YaBB.cgi?board=Questions

Someone more software skilled might be able to extract some of it.

The phase response might be tricking the VNA into aliasing your measurement.

It might give you a better unknown thru cal.