Curve puts tone into blackpoint on Digital Neg

My curve is producing digital negs with some residual tone in the blacks.

I used a solid black background for my test charts, but ink is still being laid onto the Pictorico film.

Looking at the curve numbers, all the ink channels are at zero at the absolute black point. Whenever I have seen this before it has been because the Yellow channel had positive values at the black point and it has been easy to zero out. But this time I can’t see where the problem is.

Here is the curve - would appreciate any suggestions.

PtPd_Fe2_2023_02_16d.quad (8.2 KB)