I own a Delta 12.5" surface planer and have recently noticed that the
unit is cutting unevenly.
If I were to run a piece through the right side of the cutter head,
than run the piece again through the left side, more material is taken
off. If I reverse the operation, run a piece through the left side of
the cutter head and than again through the right side, no additional
material is taken off. I thought the knives might have worn unevenly,
so I rotated them and got the same results. The OM does not even
mention any type of adjustment for the knives as they are indexed and
should not move. The infeed and outfeed rollers appear to be level.

Any ideas what could be causing this and how it might be fixed?