I am inside the brewery with Travis but I cannot kill Bull or Gouger. They seem to be marked as essential, as when I kill them they simply just lay down for a while then get back up good as new. I don't really want to use the console or cheat by modifying the quest stage, is there another way to get around this bug?
For me, the issue was that I was playing on a 144HRz monitor and things can get pretty weird when playing at >60HRz on the Gamebryo engine.
I temporarily lowered my monitors refresh rate back down to 60, loaded a prior quicksave before I entered the brewery, and was able to kill Bull and Gouger.