Thanks! Really happy with any feedback :)
Did you use the Alpha Key to upgrade your armor? (It gets purple instead of orange, for reference). Like, the key unlocks the device that upgrades Uno's armor to get through tougher ducts, but you'll have to find the device first. It looks like the restoration chamber from any save room but orange instead of purple.
There's another area acessible after the tougher ducts. The Junkyard can be reached at this point but it's not related with the Alpha Key.
Did you get the Portable Heater, by any chance?
Have you visited the Light Room in the Factory?
You have visited the Engine Room to eventually get the Alpha Key, right? Maybe you should visit it again to change the direction of the blue lever and see if something in the factory changes.
There's actually two entrances to the ducts from the factory. The first one that links the Factory with the Test Dorms, and the second which can be accessed after unlocking a specific room. That locked vent on the ducts between the Dorms and Factory can only by opened from the other side, and serves as a shortcut.
The game gets slightly less linear at this point haha Will try to give hints but i can just say the solution if you want to.