I have a world installed in 1.17.30 with experimental caves and cliffs set to true (I am not sure if that makes me run 1.17.40.23 Beta as it shows nowhere?) now transferred to 1.17.32. I spent some time building and stayed at more or less the spawning area with +- 6 chunks I guess. When I now left my home and made only about 10/15 chunks south all halfslaps that where placed on the lower part of a Block missed. They not only didn't show up but I was able to fall through. Closing the Server and restarting it solved the issue.