[spoilers]- getting to the area the first time, and arriving at the dumpster he spawned. But after dealing with Frank, you need to talk to Johnny again but he doesn't spawn in, so I can't complete the quest.

I've tried leaving the area, reloading the game at this point, switching quests, still won't spawn in to talk to him.

Edit: So I had to reload to a previous save before starting the mission and it worked.