I’ve reported this using the in-game system, but was advised by the GM’s who assisted me during my initial round of ticketing that I should post on the bug report forums.
I completed the quest “Testing the Metal” in Aszuna back in the Legion days and was never awarded the Rank 2 recipe for Battlebound Hauberk. The fix, per Wowhead, is to purchase the Forgotten Patterns of the Broken Isles book in Dalaran (vendor Ranid Glowergold) which should teach the missing recipe. After buying and learning the book twice, I can confirm this did not work for me. I have no avenue to learn this recipe now, and it is preventing me from learning the Rank 3 version as well.
