Save files ‘mashing’ together

On only one of the worlds I own, a split screen survival, I can save the game just fine, except that getting back on will occasionally contain some characteristics of the previous save. 
Note: this bug was also present in 1.19

Examples:

I am at point A, go to point B, and build a house. I then save the game.

What should happen:

I return to the world at point B in my house.

What actually happens:

I may return at point A, but the house still exists.

OR

I return at Point B, but the house is not there.