I died in a hardcore world, quickly deleted it (manually, because the "Delete world" button doesn't work) and went to create a new world. Then I saw that the normal background image was replaced by the death cam of my previous world. Also, pressing ESC on the world selection menu would show me the death screen of the deleted world. During this whole time I could hear sounds playing from the deleted world. I could repeat this process over and over again, so I recorded a video which is attached to this report.