DNS is often like that for me as well :-) But, yes, the DNA in Seveneves involved a huge amount of handwaving to arrive at the story that Stephenson apparently wanted to close on.

That. Right at the end of the first part of the book - when some of the DNA Stuff (put that way to avoid spoiling) is when I sort of mentally check out. It was especially annoying because it could have gone somewhere more fun if less... I don't know what the term would be, mythic, maybe? I think he was going for some giant over arching plot that spanned the book and that desire created the need for a bit more hand waving then I could handle.