Windows 10, java 17
There should have been visible, tangible cobblestone fences there.
Some Cobblestone fences are invisible with no hitboxes. Tried placing other blocks but couldn't.
Steps to Reproduce:
1. make a world in 1.7.10 and place cobblestone walls in a square. Say 25x25 to be sure.
2. Close world and game and reload game and world in 21w44a
you should find some of the walls are acting strangely
MC-239857 Fences, iron bars, and glass panes often use an incorrect block state after conversion