The XML files contain many spelling errors. See Planet "Sarrow" in PlanetDefs.xml for example - which should clearly be "Sorrow" given the other planet names in that system.
There are also inconsistencies in naming conventions - some techs have "Tech" stuck on the end of their internal names while others lack that suffix.
DefenseSystemTech for Defense Systems
WeaponsSystemsTech for Weapons Systems
Note the inconsistent plurality. These should have been:
DefenseSystemsTech for Defense Systems
WeaponSystemsTech for Weapon Systems