system
A chat on subreddit /r/wallstreetbets
human
The danger is the early exercise risk on the short side once you sell the box (the price difference is smaller than box width leading to instant loss). This strategy is riskless only for European style options (where you cant exercise early).

gpt
In fact, for stocks with high shorting fee early exercise happens all the time. 
  
 There are papers online that explain the math.