Chunks disappear/get swapped or are reverted to their original state

Hello everyone,

upon loading my beloved survival world certain chunks seem to be out of place (see pictures). Is there a known reason/solution for this? 

While spawning some of the "starter advancements" started to pop up, even though I already got those when I started the world a few months ago. 

The log of that game run can be found below. It is the first world I opened that day (Utopia 2.0).

I experienced this in earlier versions as well and always found it to be extremely frustrating to see all the hard work gone in a blink of an eye. 

Greetings

Schokoglurak