When trying to place a block it does not register. It simulates an invisible block. When mining a block it "disappears". There is no traditional animation of it being destroyed. If you try to place another block there the old one reappears. Sometimes if you do nothing and wait for about 10 minutes the mined block appears as it should,  ie floating. When you try to pick it up you need to stand for another 10 minutes. World killer level problem