There are times when the Threshold Icons are blank and missing their respective textures. I've noticed this in the past when the icons are tied to items, specifically, due to how WoW loads item information asyncronously, so this issue has been limited in scope to healers and potions/Chillglobe until now. A /reloadui corrects this issue 100% of the time.

Recently I was informed that this issue has also been spotted on Balance Druids.

This appears to have been fixed due to my refactor of spells and cleanup of healers.