We are several players who has lost partial puzzle solves lately due to autosave not working.
JR mentioned the other day having problems too. Today Jnicol asked if others had trouble with autosave. Hoglahoo, Janelle and IconMaster confirmed the problem.
hoglahoo: It has apparently been disabled/broken since a recent update
It dates back to around 8 march where I was working on a hard geography puzzle and my part solve were gone when I reopened it.