When creating the item, if I "Add a Spell" and choose Armor of Agathys, the item returns an error whereby I can't publish it as it has some content data or something in it that stops it from being published. I definitely own the spell, but I think I have discovered a bug. When I remove the spell, the error disappears. When I add the spell, it returns again. It doesn't affect the other spells im trying to add to the item (absorb elements, ice knife, shield, sleet storm and mirror image) (the item is called Staff of Icebound Fortitude, themed around cold and defense).

• This homebrew Item has data mapped to it that is licensed content or private homebrew. This typically occurs when licensed or private homebrew spells are linked to the Item.

It's not a free spell.

Only the free stuff can be mapped to homebrew. This is because the homebrew system isn't set up for what happens if somebody adds homebrew to their collection with non-free spells they don't also have. I believe this is being worked on (but likely low-priority).

You don't need to publish it for your own use or for anyone in your campaign to use it.