We don’t really need that leftmost bit in the reference solution: since we don’t care what the fourth ball does (it only needs to reach the bottom to be part of the output), we can send it through the second bit again. Avoiding that bit saves a whopping five ramps on the path that was intended for the fourth ball.
I think you need an extra ramp underneath the leftmost crossover.
Thank you, fixed. I built this one in the simulator, which unfortunately doesn’t complain about longer drops, so I missed that.