Currently the achievements for Hero forge are only staying updated if you keep the item in you inventory. For example: I put on 2 pieces of Valiant Leather Hero's Forge armor into my armor and get the check mark for having completed it. Then I take the pieces out of my armor, put them into my house for storage, but then, once the pieces are out of my inventory, the check mark indicating that I had collected that piece disappears. Only if I finish the achievement will the check mark stay, With the check mark disappearing, I am unable to see what pieces I am still missing to finish the achievement. --Viirus Steelhart Drinal
I noticed this over a year ago where I have to have the entire set on my character then it will update and stay completed. I don't think this is a bug but how it was meant to be and for some reason is just now showing correctly.
This isn't ideal but I think it works this way because it's taxing to search real estate for achievement requirements. You'll have to keep the pieces in your house, and put them all in your inventory once you have a set to finish the achievement completely.
