I don't know how and when it happens (random ?) i didn't find when exactly and why. But when you enter in a end portal, you can fell in the void. Chunks not loading and you die. It was on a multiplayer server.
It happenned to a friend when he used the nether portal (But It didn't do it for me).

(Can't have screenshots -> I prefer do /gamerule keepInventory true, it is safer than F2)