Lithium battery pack DIY thermal runaway close call

While building a lithium ion battery pack one welding event drilled a tiny hole in the can of a cell triggering scary reactions. No explosions or fire luckyly. The welding probe slipped from the nickel strip moments before the discharge. With such bad and moving contact, the welder made a big spark that caused the damage. The affected cell released a tiny amount of smoke and started dripping electrolyte. That cell, and those in the same parallel section, heated up to around 40 degree celsius at the surface before calming down and going back to 17. I managed to extract most of the unaffected pack and the BMS while things were calm before putting the 16 cells near the affected one in quarantine. The pack was made of 128 LiPo cells 21700 16s8p with a 200A BMS. It was supposed to be capable of delivering 14 kW peak with around 7 kW continuous current. 14s8p cells were arranged in honeycomb with plastic spacers, bonded together with silicon rubber. The remaining 2s8p were placed undernea