As a temporary work-around, if you have the latest version of the Unity Console for POE2 (https://www.nexusmods.com/pillarsofeternity2/mods/2) then you can remove the effect via the "Remove Effects" option, which can be found by going into Xoti's character sheet (the mod menu options change accordingly), then scroll down past Add Abilities, Remove Abilities to "Remove Effects". Scroll down through all the effects Xoti has on her. Magran's Leaping Flames is probably near the bottom of the list if it was relatively recent.
This happened to me after going through the Ashen Maw. I had a huge negative buff timer on it, showing -2657 seconds and getting more negative. Anyways, yay for the modding community!
