The Facility: what players are running into
The Facility is the second pathway, the sci-fi one, and it is where the forum goes quiet about strategy and loud about problems. Some of them are difficulty. A few are things that look broken. This page sorts one from the other.
The room before the Facility boss
The grey room
The most repeated puzzle is a room on the map right before the final boss that never counts as discovered. One player describes it: “Then the map shows an unidentified room right before the Boss with 3 ways in (from each side).” They lit the fires and still could not get in (in Steam discussion: Secret Room in the Lab.). Another had visited “several dozen times” and beaten the boss as both the Janitor and the Activist without it changing (in Steam discussion: Undiscoverable area in The Facility?).
Accounts of what makes it register disagree. One player says that room “was undiscovered by me and got revealed only after I visited all three rooms right before it”; another did all three, every path and every robot unlock, and is “not sure if it’s a bug or something undiscovered” (both in Steam discussion: Undiscoverable area in The Facility?). One reply calls it a bug outright: “The room before the boss is a healing room but you never get credit for entering it.” (in Steam discussion: Secret tunnels?) Two players tie it to the robot on the way, Robert to one and Roger to the other: giving it something can read “you’ve learned something” and the room then shows on the map (in Steam discussion: Secret Room in the Lab.). What Robert does is on the Robert page.

Why it matters: Urbexer
Players connect the grey room to a hidden achievement. Steam lists Urbexer with no description and 2.3% of players holding it, and one player in the bug forum writes that the zone leading to the final boss is “unmappable and thus nobody receiving the achievement for fully mapping the place out” (in Steam discussion: A Bunch of Bugs - With Screenshots!). Another notes that a percentage that low proves little either way, since some players cheat achievements (in Steam discussion: Secret Room in the Lab.). The game does not say what Urbexer needs, and the developers have not said whether the room is meant to be enterable, so treat “map everything” as a player theory. The full list is on the achievements page, and the Forgotten Path equivalent, Spelunker, is on map and pathways.
Why runs end there
The developers put it in their own words when they explained what 0.6.39 was for: “our biggest focus with gameplay tweaks has been to address the feedback that The Janitor and The Facility are too challenging or complex for most new players.” (in Steam announcement: Shroom Patch Notes: 0.6.39) One line in the same notes pulls the other way: “The Facility Explore danger scales a bit faster.”
The forum reads the same way. A thread titled “The game was pretty cool, until I got to the Facility” is from a player who dies on the boss’s last form with the Janitor and is thinking of leaving; replies say the Janitor is consistent once you know the kit, that the Life Support foresight is a trap, and that you can skip phases by killing the main body instead of the arms (in Steam discussion: The game was pretty cool, until I got to the Facility.). A reply in the same thread offers a shortcut: “Grab a Frog Tonic and keep it until the final boss, you can forget the Horror and just ignore its mechanics entirely.” The full fight, and the Stubborn trick, are on the Gunk Worm page.
One player reports a harder time with the Activist. Having beaten the Facility with the Janitor, they write that the Activist “cannot just vibe through the lab in the same way”, and that across a dozen attempts at the boss’s third phase they “got extremely varied results”, quitting to the menu before the death animation to retry (in Steam discussion: Lab is too RNG coded). Builds that get through are on the Activist page.
Softlocks and data
Two Facility-specific problems come up. Rerolls on a Facility campground reward locked one player on a selection screen with no cards; that whole family of bug is on the Dice page. And shops in this pathway take data, which players say is easy to run short of if your deck is not built for it; where data comes from is on the Janitor guide. The two maps are compared side by side on map and pathways.