I don't know why the liches in two different places had different resistances. Different sub-species?
That underground place hear the church.... that wasn't by chance just to the north east, with the stairs mostly obscured by a clump of trees? This is the place of sacrifice for the holy item quest. By opening the tombs of the guardians, you have broken the quest. There is a not-very-stern warning in the book in the basement of the cursed Abby which tells you not to disturb the guardian's sleep.
There is a fix for this, however, which I should posting an updated version of later tonight.
