I believe I cracked the safe today on my final attempt. I got the achievement. However, rather than a prize, it said, Oh no. Something went wrong. Try again. I clicked again, and it said, you already cracked the safe today.

I cracked the new safe today.

Even though I was next to the real result before, it didn't say "1 close" then.

more disturbing: AGAIN not the book as prize I cracked the old one so often over the past years and all of a sudden it stopped rewarding the book! (plus gave much less in sP)