title_body: My ESC in my stack just randomly exploded, any ideas why?
upvoted_answer: From your description I assume that the ESC in the stack blew up, not necessary the FC. This makes most sense as that is the part where the biggest currents are flowing.
  Check if the electrolytic capacitor on the battery connection of the ESC still is properly connected as that absorbs the voltage spikes your motors generate during flying. If that capacitor is loose or located too far away, the voltage spikes can destroy the FETs on your ESC and you will burn up the ESC and the motor connected to that ESC.