It applies to every spell I tried so far ( heal and mind reading ) and by using them outside of mansion I mean in the slaver's guild or after the fights, to see the specific stats of the people you capture
As for the save it happened on every game I made, I even reinstalled the game after deleting everything and it still didn't work.
On a side note I made a sandbox game with researcher background to test a bit more and on day 1, no spell worked.
The console returned
SCRIPT ERROR: healeffect: Invalid get index 'health' (on base: 'Nil').
At: res://files/scripts/spells.gd:216
SCRIPT ERROR: healeffect: Invalid get index 'health' (on base: 'Nil').
At: res://files/scripts/spells.gd:216
SCRIPT ERROR: feareffect: Invalid get index 'cour' (on base: 'Nil').
At: res://files/scripts/spells.gd:265
SCRIPT ERROR: mindreadeffect: Invalid get index 'origins' (on base: 'Nil').
At: res://files/scripts/spells.gd:184
( It also seems to happen after reloading a save )
And here's a save, I'm not sure I can give you much more informations than that.