If a node is slow to process a transaction compared to the rate at which transactions are received, it is possible that transactions in a chain are recorded in the wrong order. This can result in multiple unconsumed states in that node's vault for the same evolved state.
For example, with the following transaction chain:
– txX --> State A -- txY --> State B
If node 1 creates these transactions, and node 2 receives them as part of the finality flow, then it is possible that node 2 ends up recording states for txY before txX if they are received quickly enough. Recording txY leaves State B in the vault unconsumed, while recording txX leaves State A in the vault unconsumed.