The Nicole training bug can be fixed by correcting line 75 of nicole.rpy (in the game\modules\00core\minor_characters\nicole folder) to use "_first_visit" instead of just "_visit" as follows:
But, once you've already started the game, you'll have to type or copy&paste the corrected line (above) into the console (normally opened with <Shift-O> & closed with <Esc> or command "exit" [without quotes]) to add the action to the bottom of the living room actions list. Or, if you've already called her there, you can type "jump nicole_first_visit" into the console.
Code:
living_room.action_visit_nicole = living_room.add_action("Train Nicole to be Your Teaching Aide", label = nicole.short_name + "_first_visit", context = '_contact_other', condition = "living_room.is_empty and nicole.can_be_interacted and nicole.has_tag('available_today') and not nicole.has_tag('teaching_aide') and nicole.teaching_aide_training_available and nicole.fixed_location is None")