Hello,

I have mirrored this report as a regression bug report in our github repo, you can track its status here:

• https://github.com/telerik/kendo-react/issues/2531 

Regards,
Vessy
Progress Telerik

Hello Ryan,

Thank you for reaching out to us.

I was able to reproduce the issue using the example that you shared and we will definitely look into it.

As for a temporary workaround, you can use "null" as the initial value and add the array once you have the nested PanelBarItems:

  const [items1, setItems1] = React.useState(null);
  React.useEffect(() => {
    setTimeout(() => {
      setItems1([<PanelBarItem title="Test" />]);
    }, 1500);
  }, []);

  return (
    <div className="panelbar-wrapper">
      <PanelBar>
        <PanelBarItem title={"Projects"}>{items1}</PanelBarItem>
      </PanelBar>
    </div>
  );
};

Regards,
Konstantin Dikov
Progress Telerik