issue :
npc 8126 (Nixx Sprocketspring) and npc 8738 (Vazario Linkgrease) are training Goblin engineering schematics. But a Gnomish engineer can learn from them.
npc 7944 (Tinkmaster Overspark) and npc 7406 (Oglethorpe Obnoticus) are training Gnomish Engineering schematics. But a Goblin engineer can learn from them
How to solve :
The 'TrainerSpell' fied of npcs 8126 and 8738 should be set to 20222:
http://db.vanillagaming.org/?spell=20222
The 'TrainerSpell' fied of npcs 7944 and 7406 should be set to 20219:
http://db.vanillagaming.org/?spell=20219
Concerning Blacksmith, I think it's correctly set.
example : npc 5164 has TrainerSpell=9788 (Armorsmith)
Concerning Leatherworking, I didn't look, let me know.
(edit, they are not set correctly too, see comments below)
I don't remember if there are other specializations in Vanilla, can you tell me ?