Playing as a Khajiit Vampire Lord.
I have favorited my Night-Eye and Vampire Lord transformation ability. When I turn into the Vampire Lord and decide to revert back to my kitty cat form, my beloved Night-Eye that was once in my Favorites menu (d-pad menu) is gone.
I'd assume since they are both "Power" spells it may interfere with one another, but what do I know? I just made an account to post this bug for y'all.

I see this bug from the beta hasn't been fixed either.

Has yet to happen to me but meh I degress. I just get lag worse than even last patch caused now.

Sounds very similar to the werewolf perks "Beast Form" and "Ring of Hircine", though you just need to re-equip the ring after you tranform back to "natural" form. The favorited "Ring of Hircine" still needs to be favorited after the transformation. Both are annoying, still.

This keeps happening with my Vampire Drain ability but in relation to progressing through vampire stages, which is odd seeing as it's an ability all levels of vampire have...

I feed, go to stage 1. When I reach stage 2 it will be unfavourited, same will happen if I go back or forward a stage each time. It's very annoying.