Yeah there's something weird going on with it, I recommend checking that Lathander's passive is active in the spellbook because I've noticed in my current Honour playthrough that the passive just randomly turns itself off from time to time.
Unfortunately I do not know exactly why because I can't properly test bugs in this mode, so instead I just dragged the passive directly onto the hotbar to ensure it always remains active.
My only guess is that those Shadows casting that light-sucking aura somehow turn it off, but I never saw them extinguish the mace before Update #5.
