@NovaRain Thanks for checking.
Had another look and apparently it is a script bug that gets enabled by sfall.
This is the code
critter_rm_trait(dude_obj, 0, 76, 1);
critter_add_trait(dude_obj, 0, 77, 2);
And the error is to set the added trait to rank 2 (should be 1).
However, this does work...