While zombies don't get directly boosted toward humans, they do get launched up high from explosions. The zombies then ride up even more knockback from any hitscan, and either air strafe their way to effectively be boosted toward humans, or humans (and especially sentries which are most front) from in front will shoot them toward the humans at the back.
Flare guns and explosions from rockets, grenades or Scorch Shot usually cause the initial boost so reducing zombie knockback to not be launched above like 120-200 hammer units would help prevent this. Making a way for bullets to instead deal more horizontal rather than vertical knockback in the air could also help.
I could not upload the clips directly to the website for some reason so I made a short compilation of boosting examples here:
There are definitely better clips out there that had more deadly boosting but these are what I had.
I had !hideteam on so it may be harder to see what happened.
Flare guns and explosions from rockets, grenades or Scorch Shot usually cause the initial boost so reducing zombie knockback to not be launched above like 120-200 hammer units would help prevent this. Making a way for bullets to instead deal more horizontal rather than vertical knockback in the air could also help.
I could not upload the clips directly to the website for some reason so I made a short compilation of boosting examples here:
I had !hideteam on so it may be harder to see what happened.