When I was playing in my hardcore world my computer went flat I plugged it in and when I got back on Minecraft it said i got got 2 advancements that i had already gotten when i went into my advancements it said i had gotten just those advancements and non of the rest of the advancements were there and even some of the pages were not there when i was investigating i restarted minecraft and it was still there i have taken some screen shots.