I've searched every inch of the town you spawn into, all four factories, and the boss area along with most of the map and the final entry does not see to be there at all. I feel like it should have been in the hidden room in the final factory on the way to the site of power but there was only chests in there.
Same issue here.... Found the other 4 but the 5th eludes me.
problem occurs on offline mode as well. I couldn't find the last (5th) entry