Creating Filter, it deletes old created Filter

I would see this as a Binding issue which @jacob.small has posted about before here (Element Binding in Revit )

This AU session should help you get a better understanding on the issues at play: https://www.autodesk.com/autodesk-university/class/Getting-Good-Stuff-Out-Pandoras-Box-Element-Binding-Dynamo-Revit-2019

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