In the event that an error reading "the {field_name} attribute is not the correct type" appears when a form is launched in runtime, it may be signalling that the footer calculation for the listbox is an incompatible with the column data type.

In this example, an entity selection listbox with text type data in the first column generates the error.



Opening the first column's footer properties, the footer calculation is set to "Sum". This causes an error because the sum calculation is incompatible with the text type data in the column.



it can also be a good idea to make sure all other comparisions and meta expressions related to the listbox column are free of any type incompatible operations.