Playing on versions starting from 1.13 ending with new versions 1.16.3, I came across a bug the essence of which was that when you leave the world and go back to it, the chunks begin to change regardless of whether they were downloaded or changed earlier, they will change places with other chunks and this bug works both over the network (provided that the server is not round-the-clock) and in a single world, perhaps the bug only works on weak PCs.

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