After reloading savegame spell success chance drops to 0%

[Reskal]

Playing Alpha v0.10.21.
Topic is, that im really sick with 3 diseases (dodging training with rats) and i created a cure-disease spell with a chance of 3 base and +2 each level. I'm lvl 16 so sucess chance is 35%. After several casting fails and savegame reloads(not much mana) the spell should work, but: the first time i cast it in a location it worked at once, but if i reload the savegame and stayed there, chance dropped to 0, i tried 20 or 30 times but never had a successful cure of my diseases. When i reload the save and changed the room, no help, but when i left the building, first try cured me.
So obviously another map changes success chance of this spell.