The test (and NumOwnersNodeStopInSequenceTest as well) uses StateSequencerUtil.advanceOnInboundRpc(), which replaces the PerCacheInboundInvocationHandler and rewires all the components.

The problem is that rewiring StateConsumerImpl causes it to create a new SemaphoreCompletionService, but there's no synchronization when reading the field, a "background" task could finish on another thread and release the permit on the old SemaphoreCompletionService instance.