Niagara UI Renderer | Free Plugin for UE4/UE5

Hi Thanks for a great plugin.

My team have installed it for a project and are testing it out. The effects are working great, but there is one problem I am experiencing. I wonder if you can shed some light?
I add a NiagaraWidgetSystem to a widget, add the Niagara System and remap materials, all works fine.
However, even though I save, after rebooting UE4 I get this error:
Failed to load /Script/NiagaraUIRenderer.NiagaraSystemWidgetReferenced by WidgetTree
The NiagaraWidgetSystem is no longer in the widget.

I would be grateful if you could let me know how I can solve this.