When a gravity block falls, the block is still there, and it duplicates itself. A ghost block is left behind at the original position(before fall), and if you update the block it will re-appear, duplicating the block. It broke my redstone machine. Detailed description is in attached video.

Video:(too big to attach)
https://drive.google.com/file/d/12N5334rJhYJ80LwJcwcwFV786CNzpRtf/view?usp=sharing