It was the latest mobile version (I play on a tablet), and I was continuing with saves from previous versions. This message only appeared on paths where the massacre had happened and Oswin was dead but Sal was still alive. Whether you choose Sal or Bensen at the mill doesn't seem to affect it, it will still come up with this message, and the route doesn't seem to matter either (except for Sal, for hopefully obvious reasons).
So the paths were listed as "???", which I had just assumed was because another path split was coming up and the saves didn't know what to list. I didn't mention it to begin with since 2/3 of the massacre saves I loaded with "???" worked (Both Oswin/Sal live and Both Oswin/Sal die), so I wasn't sure whether it had anything to do witht the error. I'll try starting that path again and see if that fixes it.