If the existing design was so good, why did they have to redesign it AND increase the ventilation? Imagine if someone was standing on the platform when the battery exploded, throwing the compartment cover, metal shrapnel & burning bits of lithium metal in their face. It could have happened. Or if it happened when stuck in a tunnel which fills with smoke, 100s of people get smoke inhalation, they manage to evacuate but the subway car catches fire and is destroyed...
CRRC is the world's largest manufacturer of rolling stock, majority owned & controlled by the People's Republic of China government. According to wikipedia, they are under US sanctions as a supplier to the People's Liberation Army, and Americans are prohibited from owning any of their stock.
How can the world's largest manufacturer of rail cars, from the country that manufactures virtually all the batteries and all of the charging circuits, not have a bulletproof design for a battery & charging system? They must use them in China too...