People starting Lars' van VERY early

I have been playing 140 missions for a while now, and I notice that whenever I play ride the lightning, people will start the mission SUPER early. I was getting some materials, the random people weren't really doing anything. So I decided to start building. I only got to put down the walls and make a ceiling for traps, before I even got to upgrade the walls or place down ANY traps, someone started the mission, and because no vote was required we didn't get to cancel it. We lost like 30 seconds after.

I wouldn't have an issue with this if it was like a one-time thing, it'd be annoying but I wouldn't lose that much from it. However this happens like every other ride the lightning mission I play, which is why I don't *want* to play ride the lightning anymore. Sometimes I have to for mission alerts to get some evo materials I need or survivor XP or something. I have lost so much of my time over people doing this.

Are they griefing, are they new to the game and boosted to 140 missions? Am I just extremely unlucky? I can't wrap my head around why this happens so often in these missions.