Occurs in Fiber with multiple instances of the React package (which can't share current owner).
returnFiber: Fiber,
    current: Fiber | null,
    yieldNode: ReactYield,
    priority: PriorityLevel,
  ): Fiber {
    if (current === null || current.tag !== YieldComponent) {
      
      const created = createFiberFromYield(
        yieldNode,
        returnFiber.internalContextTag,
        priority,
      );
      created.type = yieldNode.value;
      created.return = returnFiber;
      return created;
    } else {
      
      const existing = useFiber(current, priority);
      existing.type = yieldNode.value;
      existing.return = returnFiber;
      return existing;
    }
  }
  function updatePortal(