I was going to ask a similar q yesterday when I couldn't 3* 9-4, trying to manually route them instead of using auto-run by timing the switch nodes at specific directions in the hopes of making them go different paths (not knowing that it was all RNG anyway) but kept missing 1-2 pest nodes. I did 3* it after 25 tries. The OCD in me almost made me want to pull my hair in rage.