When I entered my save again, I found that I was born at the beginning of the birth point, rather than the birth point I created last time. I found that in this archive, I found that all my backpack items had been emptied, and all the items in the box (including the ender chest) had disappeared, but my changes to the world (blocks placed) had not changed. I exited and re entered my archive, and found that the backpack items had returned to their original state, and the birth point had again become the birth point before the problem was found.

The size of this save is about 141.6MB