Assume that you are delighted with the build surface and have tried on different areas of bed. Would definitely try stepping down 0.05mm at start of print to ensure a bit of elephant's foot and that everything is properly squished.
If the slicer is really in line of fire then how about checking the G-code on the straight bit?
1) Slice with zone in question over origin so can search in code for moves around X0, Y0;
2) find the perimeters corresponding to the delaminated straight area and note length extruded, Z height and extrusion amount. Should all cohere.
That would at least eliminate S3d (or not).