Observed behaviour: the in-game dialogue says the river plug in the Cloakwood Mine is made of steel, but the journal entry says it's made of obsidian (i.e. volcanic glass).
Expected behaviour: I don't think it matters which it is, but the dialogue and the journal should agree. The on-screen appearance looks much more like steel than obsidian, so I suggest the journal text is the one to change.
Comment: yes, I know this is trivial, but it's clearly an error so I thought it best to record it.