Well that only took about 2 years to figure out, lol.
I finally figured it out by tweaking the Fabrik framework code so it still pretty printed the requirejs setup when not in debug (usually we just render it all in one big long line rather than pretty printed if not in debug), copying that entire script section at the bottom of the doc that does all the requirejs magic from a debug and non-debug render, pasting them into two text files and using WinMerge to spot the differences.
As soon as I did that, it sprang straight out. The shim was using viz/fullcalendar/fullcalendar as the dependency, but the require path itself for fullcalendar had the -min on the end.
-- hugh