Witch demon form not working with 3 persistent buffs and support gems

I've got 3 persistent buffs active: grim feast, blasphemy, and withering presence. I've also got 3 support gems slotted: clarity, cannibalism, and despair (for blasphemy). I have all the spirit required for the buffs and any support gems I have slotted (only need 145 spirit and all the skills show they are active in my skills panel).

When I try to cast demon form, nothing happens (no audio queue, no message). When I unequip a buff or ALL the support gems for those buffs (doesn't matter which buff I unequip), I can cast demon form, then equip that same buff and things work as expected.

This only happens when I have 3 buffs equipped (2 buffs and less works fine and I can't test more than 3 buffs yet).

EDIT: The bug isn't with demon form not working properly - seems to be a UI bug. I had the vitality support gem slotted into the demon form ability (which I didn't realize used spirit). Vitality uses 20 spirit reservation, but all the abilities still show as active and the spirit reservation meter doesn't properly display. The spirit meter shows I am only using 145 spirit, but I'm actually using 165.