Help needed CITIZEN CL-S521 Problem printing labels?

Hi there I wondered if someone would be able to help? We own a CITIZEN CL-S521 and have this attached to a Mac with the macOS CUPS driver installed. The printer is loaded with 4” x 6” labels. When we print or Royal Mail click and collect labels to the printer the print is cropped off. Please see attached. This happens regardless if scale to fit / 100% etc is selected? Has anyone had this issue before or happen to know how to resolve? Many thanks in advance, Steve.

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