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Yes, this has happened before. I think it's a combination of the mirror mode and the Overlord Hub. In the mirror mode, different artifacts are first generated on the planes (as in a normal game), and then they are synchronized. At the beginning of a turn, one of the players has information before the artifact synchronization, and when the players' turns are combined after the Overlord Hub, this information is displayed for a while, but then it is overwritten, and everything continues normally.
This is just a theoretical explanation (I don't have the source code for the Overlord Hub), but it seems like a fairly convincing explanation for this situation.