I've noticed that every time my game has crashed, all my advancements that I achieved are no longer there, and I have to get them again. e.g. I have slept in a bed in this world many times, and have completed the sweet dreams advancement, but when I sleep in a bed in that same world for the first time after my game crashed, I will get the sweet dreams advancement again. This is the same for all the other advancements. This bug has been around for a while and is still an issue in 1.16.