Epson 3880, Lightroom 4 - Borderless prints ignoring LR4 margins?

Hi all,

Having a problem with my Epson 3880 when I'm printing borderless prints. I've got margins of 5mm set up within Lightroom and I'm using the A4, Manual Rear Borderless (Retain Size) paper size. I'm finding that it is still printing right to the edge of the paper and ignoring my margins. Does anyone know why this might be?

Thanks in advance,

Welly