Einstein, split in two
"Last block was a broken link. I hope this one goes better." Block 10 went up just after midnight UTC on April 9, 7 mBTC again, with one line of question: "Four words within Einstein." The format is word1 word2 word3 word4.fnw, where fnw is the tail of the block 9 key, the "broken link". German words allowed. Asked about case, the author said normal capitalization.
It sat there for hours. Update 2 splits the word for you: "Break up "within" into "with" and "in"." Update 3 starts with "Damn, this was supposed to be easy." and says to google "with Einstein". Google answers with Joshua Foer's memory book, Moonwalking with Einstein.
So two words go with Einstein and two are in it. With: "Moonwalking with", from the book title. In: "ein Stein", a stone in German. The string is Moonwalking with ein Stein.fnw, then SHA-256, entropy, m/44'/0'/0'/0/0. One commenter didn't buy the capital S as normal capitalization. They had tried a lowercase stein.
The same line break again
After the author posted the solution, two players wrote that it didn't give the right key. The final update says why: "my mistake in hashing block 9 happened in this block too. Again a line break at the end". Almost eight hours after the claim, u/Crypto_Rachel spelled it out in a comment, the answer "with a new line", then the address, the public key and the WIF.
Funded at 00:18:53 UTC on April 9, two and a half minutes before the post, and claimed at 01:42:12 the next day for 679,456 satoshis. The author wrote that the solution went to the closest comment. u/Agelais wrote at 01:39 that they had received the answer, and the claim confirmed two and a half minutes later. Close, but the chain doesn't name anybody, so the record says solved and names nobody.