Before doing this I had aligned a bandsaw and it had no horizontal error, in fact I used straight tubes. Based on that I expected the beltsander to need no horizontal offset but it actually needed quite a bit, close to half of the range of the eccentrics. My current thinking is that the offset I needed is because something is wrong.
I'm using standard eccentric tubes. I'm using the 'mystery bolt' but I confirmed it makes no difference whether it is in or not. Sanding belts are tracking correctly. I've disassembled the sander at the trunnion and don't see anything wrong. I didn't see anything in the manual that would relate to this behavior
Any ideas what would cause the sander's alignment to change when it is rotated?