Some things I tried. https://kansasrailroads.tiddlyhost.com/#%24%3A%2Fcore%2Fconfig%2FGlobalImportFilter - I changed this filter to just [all[shadows+tiddlers]tag[$:/tags/Global]!is[draft]]
and it did not help.
I added the tag $:/tags/AboveStory
to your Example Tiddler and it did not help (I thought maybe getting rendered from a different part of the pagetemplate might help).
The only thing I found which did help is opening the Example Tiddler in a new window. There the convertdate
procedure is rendered fine.