The Black Doubt Hexer's Robe + Lich's Eternal Life = Eternal Mana Drain

I'm not sure of the reason, but after choosing Eternal Life acendence Lich, if at some point I take off The Black Doubt Hexer's Robe, the life stops regenerating and the mana starts wearing off until it reaches 0.

Only resetting the passive skills (Eternal Life + Life) on the ascendancy tree solves this problem.

I'm not sure if this is directly related to Body Armor or to any of the stats.

Eternal Life prevents HP changes when Energy Shield is > 0.

If Energy Shield begins to regenerate (outside of combats or through Convalescence) when HP is not 100%, it will prevent life HP from regenerating to 100% through regeneration or using a potion. And because of Black Doubt's unique ability, mana will be reduced to zero over time.

I just don't know if this is a bug or a feature?