Like answered in the game tchat (but I think others can benefit from the info) : if something announced in game page news or on patreon feed, it means it's not ready, even as some experimental bugged build. ^^
This quest wasn't, so you enter at your own risk in uncharted territories, where you can crash or wipe your personnal datas, or even full game ones.
Not recommanded, but indeed it wasn't clearly indicated.
That said, it illustrates the fact I really build the game 'in situ', and "alpha early access" statement ('you can see the game developpement from the inside') isn't an expression : you can wander in what I'm factually currently working on and see it grows minute by minute!
(I personnally think it's ultra cool, but I'm a weird person, so what do I know? huhuhu :p)