In some rare cases, pistons can freeze a chunk.
To do this, you need to make a machine that uses pistons in the center of the world, then generate chunks at the world's border (lots of chunks) and teleport back to the machine.

Also, sometimes, for some unknown reason, blocks are strangely duplicated.

world file: https://drive.google.com/file/d/1-XuSUc_lFMx7P2S_RIlmz_cbAzG81KdK/view?usp=sharing