When I change just the x value with the vector 3 the part randomly is placed higher ?

local module = {}

NPCs = script.Parent:WaitForChild("Aliens")
End = script.Parent:WaitForChild("EndPart")
Sweeper = script.Parent:WaitForChild("Sweeper")

function module.mainActivate()
 if NPCs and End then
local move = coroutine.wrap(function()
  while true do
   wait()
   Sweeper.Position = Sweeper.Position + Vector3.new(1,0,0)
   NPCs.Alien1.Humanoid:MoveTo(End.Position)
   NPCs.Alien2.Humanoid:MoveTo(End.Position)
   NPCs.Alien3.Humanoid:MoveTo(End.Position)
   NPCs.Alien4.Humanoid:MoveTo(End.Position)
   NPCs.Alien5.Humanoid:MoveTo(End.Position)
   NPCs.Alien6.Humanoid:MoveTo(End.Position)
   NPCs.Alien7.Humanoid:MoveTo(End.Position)
   NPCs.Alien8.Humanoid:MoveTo(End.Position)
  end
 end)
 move()
  end
end

return module

What might be happening is when you use Vector3 for Position, if the part collides with another part, it will default to being above it instead of partially colliding with it. Try using Sweeper.CFrame = Sweeper.CFrame * CFrame.new(1,0,0)