The FactoryTable for the Teraton fabricator includes rows where the output is "l-2" but in the function to adjust the item's level intTeratonGetLevelCurve (line 1383 in Teratons.xml downloaded from Xelerus) there is no case in the switch block for that text. There is "l+2", but no "l-2".
Found this reading through the XML, not from play-testing. (I was trying to figure out how best to get past the mid-game quickly by gaming the system).