Downloaded the Gen 3 Event Savefile from this link -
Imported the file into PKHeX (20200807) and a bunch of boxes show up as illegal. Attached the pk file for one such mon. Tried the Auto-Legality Mod and ran into some exceptions which are attached here as well
HootHoot_legality_exceptions
163 - ホーホー - GCEA HootHoot.pk3