0.5.15d
The "Responsive" trait's increase toxicity via the tox_mod variable is handled in the tox_set function, causing your full toxicity value to be multiplied every time it is changed. My slave was stuck in a loop of getting the daily reduction in toxicity of 1-5 points, thus causing tox_set to multiply the resulting toxicity by 1.2 which caused the slave to constantly hang around 100 toxicity and mutate happily. While that would be a fun idea for a trait, it's certainly not intended behavior.
The tox_mod should probably be handled in on_potionusebutton_pressed() in scripts/Mansion.gd and use() in inventory.gd