This is basically normal behavior. On the PRO-100S, true borderless printing usually works by slightly enlarging the image so it bleeds past the paper edge. That avoids white edges, but it means a small amount of the image is cropped off. Canon’s Print Studio Pro software provides this borderless option on supported papers.

If you want the entire image preserved, the alternative is to print with borders (or very small borders) and then trim the excess paper afterward. In practice, you usually have to choose between:

1. Borderless print: no white edge, but slight image loss from scaling/cropping.
2. Full image retained: print with a margin and trim it manually.

Head calibration can improve alignment, but it may not completely eliminate tiny uneven borders at very small margin settings. Larger borders tend to print more evenly. So if you need absolutely clean edge-to-edge output, use borderless and account for the safety margin in your layout; if you need the full frame, print slightly oversized with borders and trim.