Despite refreshing and reloading data into the same object, data values which were previously within a record still appear as categories on tables and charts within the app view, like some sort of "ghost record".
For those familiar with Excel pivot charts - this is fixed by selecting a Pivot Table Options setting called "Retain items deleted from the data source" , "Number of items to retain" then selecting None and refreshing data.
If Knack can have the default at None, this would be fantastic. I cannot see a reason for wishing to keep old record values however if this feature appeals to other users then a selection option is a way forward.