This was documented a while back, but it not only still persists, but is actually even worse than first reported.
Simply put: changing anything with your character while your aura is active will set all your spellpower to zero! (or at least, stops your aura from referencing your spellpower at all). This persists until you toggle your aura off then on again or reset your character to what it originally was when you first turned it on.
Here are two youtube videos demonstrating this:
https://www.youtube.com/watch?v=KhV_1iUO_zw
https://www.youtube.com/watch?v=Hs-Y9-JzG7k
However, it's not just drinking potions (and while one video only claimed comms of valor purchased spellpower pots, this actually happens with ALL pots. Normal spell power pots from the portable hole, remove curse pots, remove disease pots, cure critical wounds pots, store bought healing pots, they ALL remove spellpower from your aura) and swapping gear. This also happens if you open a bag (ingredients bag, etc) while your aura is active to look at stuff. Don't even need to move anything around, just opening the bag sets your spellpower to zero!
Swapping from a main hand weapon to a scroll (say to heal yourself) also sets the spellpower on your aura to zero (thus you only do base dice damage per tick, no spellpower multipliers taken into account at all) until you re-equip your main hand weapon you had on when you activated your aura in the first place.
I just tested this out in a wilderness zone, so it's not a "only in public zone" thing one may suspect from the videos (it's easiest to test using the methods those people used, but this happens regardless of where you are in the game)