I think the soft lock is a result of the bonus time after what happened. I made the mistake of delivering the wrong drink while I was pressed for time and was set to a bonus of -0.50 ( Hence why one of the customers is blacked out. ) When I entered the door the game had soft locked which I almost assumed was a game over state until I waited and realized it wasn’t. Though it was like 2 A.M and I needed sleep for college so I shrugged it off, but not before saving my score.
With how Shift XXX basically removes commands to recover from a fall, this made it important for me to finish things quickly. Especially as I hadn’t really found a suitable way to slip past the other waitress. This is also partially why I used simple QTEs during my playthrough. I feel inputting 3 random directions in a row before tripping is difficult compared to pressing the same set of buttons, and much easier on a keyboard.