D4R tail and pin boards misaligned

I'm learning to use my Leigh D4R Pro and am experimenting with single pass half-blind dovetails for a cabinet project. But I'm stymied by a consistent misalignment of about 1-2mm offset between the tail and pin boards. I've checked the manual carefully and discussion seems directed at misalignment caused by concentricity when using 2 routers, so not helpful in my situation. I've checked and rechecked all the obvious steps, am confident that my joinery is up to scratch and I'm following the instructions correctly - in fact the dovetail joint itself fits perfectly, but with the 1-2mm misalignment between the face and side. I'm pulling what little hair i have left out, so any thoughts on what I'm doing wrong greatly appreciated. Thanks Charlie

So, the two boards have a 1-2mm offset right? So, for example, your sides are 1-2mm lower than the face? I think this is probably something to do with the dovetail spacer. The one that is attached to the front of the jig to the left of the board. Can't think of what else it might be.

Are all the boards the exact same width.

Any chance of a picture?

How did you go with this issue?