I'm having the same problem when trying to play the game natively through Pico-8 on PC, I run the title cart, change settings, choose 18 or 9 holes and the cart just loops every time I press 18 or 9 holes!
Same if I try to quit through the end screen 19th hole option!
EDIT for addition.
Just tried it out on my Powkiddy RGB30 natively via Pico-8 through Rocknix and it works faultlessly. NICE.