`rc-menu` blinks on horizontal mode

Hi There,

I'm running the following code:

import React from "react";
import "./styles.css";
import Menu, { SubMenu, MenuItem, Divider } from "rc-menu";

export default function App() {
  return (
    <div className="App">
      <Menu multiple key="1" mode="horizontal" openAnimation="zoom">
        <SubMenu key="1" title="File">
          <MenuItem key="1">A</MenuItem>
          <MenuItem key="2">B</MenuItem>
          <Divider />
          <Divider />
          <Divider />
        </SubMenu>
        <SubMenu key="2" title="Help">
          <MenuItem>What</MenuItem>
        </SubMenu>
      </Menu>
      <h1>Hello CodeSandbox</h1>
      <h2>Start editing to see some magic happen!</h2>
    </div>
  );
}

and there is a blinking behaviour when setting the menu mode to horizontal.

Is this intentional?

Sandbox link here: https://codesandbox.io/s/cranky-haslett-o84iu?file=/src/App.js

Start with the reproduction in src/App.js from the linked CodeSandbox, using Menu in horizontal mode with openAnimation="zoom". Confirm the blinking behavior and trace the horizontal-mode rendering path; done means the provided menu no longer blinks under the reported configuration.