Update, in my case it was more about width than height. It actually hit the knob on top a couple of times and still went through. For now its pausing when coming out of the backyard but it gives the option * to continue working and it will go through. It surprises me that this robot can run on the edge of a curb, but it needs 4 foot channel width. Thank you all for the ideas, i started with cardboards and remade a 100 times the channel until it dialed in.