That's why I have so much trouble solving it for people, because on my end, I can name it "potato" even and it works...Sorry for kinda misleading you for "track not found" error, I deleted both versions and reinstalled your last update. I still got the error so tried to add files from vastchapa1980's version one by one then deleting it, to see which one the game was asking for.
And the track launches with "Special Stage Route 5.kn5" added (190MB) (the v2.1 works too if you rename it "Special_Stage_Route_5.kn5").
@JBolho, I don't know if this file is in your folder too but it looks mandatory to run mine. I checked (opened with CM and spotted the differences, thanks to your changelogs) the .kn5 files to be sure which one was shown in-game and this is yours running.
What about the Clubman layout?