It's not autokilling, it's if you touch the top or bottom, it kills you. Just jump around, as plat you can do that.
I did that a few times, and it kept doing 125 damage or w/e and I couldn't work it out - You need to crouch jump onto the edge of the tube I find to avoid hitting the ceiling it, then just go across it.
Yea I complained about this on mantis but nothing can be done about it cause the mapper is a shithead. I always lose at least 75 health unless I luckily jump in the correct spot.