Chunks will uplift them selves or change the terrian on top.

Chunks will uplift them selves or change the terrain on top. this only happens near the player spawn and will happen after a few times of logging on. This has happened on a few worlds all with different versions, as well as backed up versions. Would be great to know to get the old world back and wouldnt mind losing a bit of progress. The inventory and everything else stays the same.