I'm trying to add Thermal's Insight enchantment to tomes but when I add the id to the list I get a tome with the right level but with the ID of the enchantment before (holding). So I have a tome with Holding III which should have been Insight III

Have you confirmed that the IDs are the same across, say, a Tome and an Enchanted Book?

Tried adding them back to check the IDs and now they are properly added ... I dunno