Sandbox: https://codesandbox.io/s/cranky-kapitsa-op3jh

Repro: type "a" and then after a second "b"

Expected: Eventually you'll see "ab" in all fields. Pending "..." indicator goes away.

Actual: You'll keep seeing "a" in low pri field. Pending "..." indicator is stuck.
};
    newQueue.dispatch = setSnapshot = (dispatchAction.bind(
      null,
      currentlyRenderingFiber,
      newQueue,
    ): any);
    stateHook.queue = newQueue;
    stateHook.baseQueue = null;
    snapshot = readFromUnsubcribedMutableSource(root, source, getSnapshot);
    stateHook.memoizedState = stateHook.baseState = snapshot;
  }
  return snapshot;
}
function mountMutableSource<Source, Snapshot>(
  source: MutableSource<Source>,
  getSnapshot: MutableSourceGetSnapshotFn<Source, Snapshot>,
  subscribe: MutableSourceSubscribeFn<Source, Snapshot>,
): Snapshot {
  const hook = mountWorkInProgressHook();
  hook.memoizedState = ({
    refs: {
      getSnapshot,
      setSnapshot: (null: any),
    },
    source,
    subscribe,
  }: MutableSourceMemoizedState<Source, Snapshot>);
  return useMutableSource(hook, source, getSnapshot, subscribe);
}
function updateMutableSource<Source, Snapshot>(