I'm having problems with vector fill patterns shifting position when I publish my file to pdf.

I'm creating a cross-stitch embroidery pattern in CorelDRAW 2021.  As part of the pattern, I'm using vector fills - which I've sized to fit into a grid.  But when I export the file to pdf, the pattern fil shifts just a little bit and then the pattern is no longer aligned with my grid.  Does anyone know how to lock the origin of a vector fill to prevent this from happening, or can anyone give me another solution that might work?