I appreciate your attention and help.
Fortunately, I found the problem was not in my Wacom Intuos 4, since all my other applications did not have this issue. That included the Vector Pen tool in Affinity Photo 1.10. Since it was isolated only to Affinity Designer, I figured a driver setting between AD and the Wacom tablet somehow got corrupted. I ended up fully removing Affinity Designer, including all registry values, and reinstalling the software. I then tested the Pen and Pencil tool in a new document, and the issue was resolved. The offset is gone, and I can now resume my work. Of course, I have to reset all my preferences and reload all my assets, palettes, and brushes. But that's an aggravation I can tolerate.
Thanks again for your suggestion!