Wrong Size after extension of Ortur LM2 Pro

I have recently changed the size of my Ortur LM2 Pro from the stock size to 80mm in the Y direction. I have changed the sizes within Lightburn to reflect the change. After drawing a 400mm x 800mm rectangle within the software, lightburn informs me I am out of the working area every time I try to frame the box. I checked to make sure I was within bounds on the screen and I am. I then drew a smaller box, within the lower 400mm half and framed that and it framed with no problem. I then moved the box to the top half of the 800mm and it says I am out of bounds and refuses to frame

This, even though my screen reflects the 400x800 working area.
Any ideas anyone?