Since Battlefield 4s release, bugs and crashes have been quite an issue for some players. There have been many reports of players multiplayer progress being lost, single player save files being corrupted and several crashes and freezes while playing. These issues are still under investigation by DICE, but they seem confident in resolving them in a timely fashion.
via N4G: pc news feed http://n4g.com/news/1385714/dice-working-on-fixing-bf4-progress-loss-and-more
via N4G: pc news feed http://n4g.com/news/1385714/dice-working-on-fixing-bf4-progress-loss-and-more