Have the coil air gap adjusted tighter. If the gap is on the larger side and maybe the magnetism is on the lower side, with thermal expansion, this will cause the coil to not energize normally and not fire under combustion pressure.
Did you ever figure exactly what your problem was. I am having the same issue. I have a 2018 Liberty Z with the Kawasaki engine. I go to cut grass it starts fine. Get done cutting and let mower sit. I go to restart it and nothing...Let it set overnight and it will start right up. Frustrating!