Occurs in Fiber with multiple instances of the React package (which can't share current owner).
if (shouldClone) {
      const clone = createWorkInProgress(fiber, priority);
      clone.index = 0;
      clone.sibling = null;
      return clone;
    } else {
      
      
      
      fiber.pendingWorkPriority = priority;
      fiber.effectTag = NoEffect;
      fiber.index = 0;
      fiber.sibling = null;
      return fiber;
    }
  }
  function placeChild(