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.
{F6584}
Here the logs :
{F6587} {F6586} {F6588} {F6591} {F6590} {F6589}
{F6592} {F6594} {F6595} {F6593}
{F6596} {F6597}