IF you wanted to give a player health boost for 1 second repeatedly for example set in a repeating command block with a delay of 16 ticks. When activated the command works and repeates but upon death, you are in the respawn screen, for some reason your character picks up the items you dropped without clicking respawn yet. If you do click respawn you will get stuck in a generating world bug. You must close minecraft because nothing else happens. Upon opening minecraft again and reentering your world all items in your inventory will be gone, the items also aren't where you died on the ground, everything is lost This isn't always the case. I found that this only happens when your player picks up the items as you are dead. Any items that weren't picked up don't get deleted. When playing multiplayer I found that when my friend dies, he leaves my world and renters but then he appears right back at the spot he was before death, with all items. Only the host of the world will lose their items when exiting the world after death. There are many benefits to giving a player health boost repeatedly rather than giving it to them forever and clearing it. Which is the only reason I came across this bug.

There is also a test world to reproduce the bug.

Health boost bug.mcworld