I downlaoded and played for about 8 hours yesteday getting to level 37 and beating default mode just to start into adventure. Once I had decided it was time for sleep I went to close via the exit menus, when I exited using that GUI for some reason it reloaded an old save from when I was level 17 and overwrote my newest save file and I have lost most of my progression. 

Its kind of BS when I spent a fair amount of time honing my preferred kit with the right enchantments to have it erased due to an error.