I think this fixes it, but please check me as this is my first time in the code. I'm guessing there was a change to the naming of "medium" difficulty to "normal". Which caused the diff variable not to be set (Nil). Which means that the function "generate_random_character_from_data" didn't know what to do. If this fixes anyone else's game who's experiencing the same issue, please reply letting us know. Thanks!
globals.gd file:
func reset_roll_data():
...
match ResourceScripts.game_globals.difficulty:
'easy':
char_roll_data.diff = 2
'normal': #'medium': <-- previous version of game difficulty? Does this fix it?
char_roll_data.diff = 4
'hard':
char_roll_data.diff = 6