Wrath of Summer is still bugged in v1.261 and can cause sync errors. When you use its ability, your Shadow Energy is subtracted 1 but if you cancel, it should be back to what it was. This is updated fine if you're using Wrath of Summer but your opponent will not see it go back up 1. So if your opponent sees you at 0 Shadow Energy and you use the ability and cancel—sync error.