Puckdropper puckdropper(at)yahoo(dot)com wrote in news:543ed973$0$39585
:

Have you run the saw without the riser? If those pins aren't just so,
it's possible they're pulling the two halves out of alignment.

Yeah, I think I'd second that suggestion. Beyond that, if
the riser block is symmetric, I'd try turning it around 180
degrees and see if that changes anything.

I'd also suggest making sure the surfaces of the block, and
the saw that it sits on, are clean, without anything trapped
in the joint.

If all that is good, I might try taking the shims out from
the lower wheel, and putting a very thin shim under the front
of the riser block (to tilt the top wheel back a little,
since it sounds like it's forward with respect to the lower
wheel).

John