It was so obvious.
This entire time we've been thinking it was teamcity, or the server, or whatever.  And sometimes it'd work on our server, and sometimes it wouldn't.  The problem was core.  The fact that many different versions of it existed at one time inside of the server, and that the ones that already existed took precedence over the one we included in Demigods.  Core needs to just become something we copy paste from, not something we automatically include in all of our projects.  The whole idea of a seperate plugin to house core is too much work for both server administrators and us.  We'll just include what we use, nothing more.