Mansion.gd in scripts folder, line 982 (line 1010 in vanilla, same code)
if (person.relations[i.id] <= 200 && !person.traits.has("Fickle")) || person.traits.has("Monogamous"): globals.addrelations(person, i, -rand_range(50,100)) else: globals.addrelations(person, i, rand_range(15,30))
This changes relations between slaves after sleeping in player's bedroom. Isn't 50 to 100 penalty too high for just sleeping?