There's a very weird system in the Orcmin labs where you first encounter a Machine Elemental with no possible way to win it (if you can't get to 18 STR). The Machine Elemental is standing right behind the closed door, so the experimental potion is accessible only after the fight for which it is intended. To add, if you open the closed door and back away, the Machine Elemental actively chases you, and you can't really maneuver around him...
Bramble Fairy doesn't always recognise fleeing.