Black Soul Gem not being made

[Scratch_]

I am at one of the Necromancer altars, on the correct day *30th of Frostfall, Eighth day interval, the light is shining above the altar so it is activated* and plenty of grand soul gems. I cast Soul Trap on the altar *first level touch variant* and it does NOT make the black soul gem. It should not matter if the gem is filled or not nor the level of Soul Trap spell. Am i not hitting the hitbox correctly with Soul Trap? Is this a known bug? I am at the Fort Istrius altar. Has anyone else got this problem?

[Calico Beard]

I've tried making black soul gems at Fort Istrius and Dark Fissure and it hasn't worked at either.

Edit: Tried again at Fort Linchal and it worked