Every time I encounter the Blue screen of Death (this will make my Minecraft exit without saving itself), the advancements will be reset, nothing is remained, you have to start from scratch to get them back.
Steps to reproduce:
Somehow getting the Blue screen of Death (or shut down Minecraft without letting it saving or auto-saving)
Log back into the world
The advancements would be reset,
This is my world on Day 112, after the BSOD:
And this is my backup world on Day 109 (notice the house, my horse and farms are still intact to prove that I'm not making stuff up), before the BSOD:
http://imgur.com/5fpWTQf
Cannot reproduce with a SIGTERM or SIGKILL.