I had similar results with the 17th not saving. I had to complete them multiple times before the puzzles from the 17th finally saved. This is ridiculous.
I have had similar issues once I was able to get it to sign me again. I left the game up for a few days and didn't lose progress, but it shut down overnight and I woke up today to the board being clear from April 10-April 19. The Microsoft team is too smart to not being able to clear the bug. Anyone have Bill Gates's phone number?