On 17 November 2021, after a Boeing 737-800 commenced initial descent into Patna from FL350, a cautionary alert indicating automatic pressurisation system failure was annunciated. When the initial actions of the prescribed non-normal procedure did not resolve the problem, the system outflow valve was fully opened, and a rapid depressurisation followed. After this incorrect action, the relevant crew emergency procedures were then not properly followed. It was further concluded that the captain had temporarily lost consciousness after a delay in donning his oxygen mask. The context for the mismanaged response was identified as outflow valve in-service failure.