My friend was the hoster of the dedicated server. I witnessed the scene in live cause I was watching just behind when it happened. He started some modifications following a misunderstanding, I told him to go back. So he did a strange sequence which I'm not really sure.
I can only assume it involved the undo and redo button for sure and maybe put a blocks line. It was like if the both were processed in same times and have caused the destruction of the blocks.
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