Hi Mike,
We are sorry this has inconvenienced you. This is a known issue that will be fixed by an upcoming patch. The problem occurs when imported layer names are considered duplicates due to leading zeros being ignored, e.g., layer name "OG01contours" is seen as the same as "OG001contours". The simple work around is to vary either the numeral or the alpha prefix or suffix in the layer name either before the step that throws the error.
David