The power is not reaching the hub on the side of the Empire. We don't know where the actual problem is on the Kislev side. Something could be wrong with the stone at Kislev, they could be draining an intermediary stone in the forest or using some wide area magic to attract the energies regardless of the network, which is why it's best to start the investigation at Kislev City.
I guess so, but that really does feel like the issue of projecting the last war on the next one, specifically the rescue of Vlag. Personally I think it is more likely that the people of Kislev have noticed the issue with their own Waystone network before Imperials on the other side of the border.