So I've counted 19 forum topics complaining about the notorious coop bug in this particular mission, and one year later it still hasn't been fixed?

Everything so far was great, but when we started "Lightning in a Bottle" for the first time, my coop friend said it was lagging heavily and then the sound disappeared completely for him. So we decided to restart and now the game always crashes for me (the host) at the countdown screen.

A note for anyone willing to complete this game in coop: AVOID.