I loaded up the single-player world I have been working on for some time. It has a bunch of buildings and pens for animals. When I loaded up the world, there was suddenly grass blocks in the middle of a sand biome and my buildings had parts removed and placed elsewhere, even in the ground. a wooden structure I had was missing a wall and the missing wall was 40-50 blocks away from it. Every time I have opened up this world, it is messed up even more. I will take the time to fix it and save but the next time I open it, the same thing happens. There are different parts in different places but it has the same effect. It is on peaceful and is an older seed although I don't know from what edition. It seems every time I load the world, it is distorted even further. This hasn't happened with the other world but I haven't used that world in a while and have not actually built any buildings, just in a village.

Steps to Reproduce:
1. open up minecraft launcher, hit play game
2. select single-player, select world, let world load
3. notice that buildings are separated and that blocks are moved