Fixed, it turns out that the "not hidden_resource" condition is bugged for precursor level buildings. As suggested here https://forums.totalwar.org/vb/showt...lding-DB-error

For the future, there should be a new hidden resource "not_italy".
For now, the semi-savegame-compatible solution is:

step1. swap the order of socit and provinc in edb and delete provinc in socit's upgrade (doesn't make sense anyway, one requires italy the other requires not italy).
step2. change condition of colony_r2_precursor to:
colony_r2_precursor city requires factions { f_rome, } and building_present hinterland_roads and building_present_min_level govrome civlib and not building_present_min_level govrome socit


And by the way, what's the region name of Syracusa after rome conquers it? I tried Syracusa and Syrakousai neither works.