I love this state machine! I did find two issues once I deleted the Top Down scripts and objects on the platformer.
"ai_vars=[0,AiState.stand,1,no_direction];" had to changed to "ai_vars=[0,AI.idle,1,no_direction];"
"ai_var[0] = 0;" had to be changed to "ai_vars[0] = 0;" for the AI to load. The AI character also cant turn left.
When I enabled "draw_text(x,y,string(dpad_dir));" on the Draw event for the Player the correct numbers appear for the directions (180, 0, 270, etc), but after moving or jumping it sets to -1. If I press left and down before jumping the character turn left before jumping but the number displayed when standing is also -1. Is the number being displayed the face_direction? If so that might be the problem.
The character will also move left after jumping (but not face left) if the left and down button are both pressed.