Yea, I ran into the same problem, so I skipped that one for now, but it seems to happen on every single Mercury Djinni. I emailed the dev about 3 weeks ago telling him about this glitch and recently, he told me that he had found what was causing the problem, but hadn't found a solution to it yet.
He should get it fixed soon-ish I would think though. So for now, I have stopped playing the game because I want every Djinni too
All we can do is wait now..