While playing in Alex's Caves version 2.0.2, I was messing around with magnetic blocks and iron items when I noticed that iron horse armor wasn't being affected by an azure magnet. After testing all magnetic blocks, the horse armor was never affected like other iron items were.

This could be easily fixed by adding minecraft:iron_horse_armor to src/main/resources/data/alexscaves/tags/items/ferromagnetic_items.json