I was staircasing to Y320 for an achievement then it was lagging a lot whilst building to Y320, and then it unlagged and then my staircase disappeared and then my totem went and instantly died before hitting the ground, causing me to lose over 200 levels and items. It only does it sometimes when it attempts to save the game. This bug makes me so much less motivated into playing survival Minecraft. Happened on bedrock edition on Xbox console in survival.

To get it to occur, first you need to be on the floor at any Y level with at least three stacks of solid blocks. Now make a diagonal bridge going upwards. At any moment, the save icon on the top right appears. Keep placing blocks diagonally whilst going upwards and when the icon disappears, the blocks that you've placed down whilst the icon was there vanishes and then you instantly die a few frames later, even with a totem with feather falling IV.

It is rare to get it to occur, but when it does, the blocks whilst the icon was there disappears and instantly dying with the death message "Name fell from a high place."

What should've happen is that when the icon appeared and disappeared, it doesn't lag the blocks and makes them disappear. Rarely, the saving icon causes the blocks to lag behind and then the game doesn't register those blocks and keeps thinking that you've fallen the amount of blocks that you were off the ground each time you place a block.