I recruited Janusk as a +1 Tech researcher. Saved the game. Came back the next morning, loaded the game and he had switched to a +1 Gildar merchant.

I recreated the issue with the two saves below. The first link is the save game right after founding my first city. If you end the turn Janusk shows up as a Researcher for hire. You can hire him and he is indeed a researcher. However should you save the game as the second link shows, reloading from that will turn him into a Merchant.

I presume this is probably linked to the same bug that causes injured units to vaporize and units to lose extra movement upon loading saves.

http://filebin.ca/cuzqux

http://filebin.ca/jfzod