Yeah, since the other things have been checked, I had thought humidity too, but more from a standpoint of causing just enough warp/swelling in the draftboard to make it not cut completely through with the default settings.
I assume you’re pinning it down during the cuts @pford ? To make sure it’s completely level? I live in a high humidity area and I have to pin everything down, even if it looks perfectly flat.
Cause it’s usually not.
I use these:
A few of these will let me cut through badly warped (over 1/8th inch) quarter inch goofgrade from Home Depot. I never have a problem with the PG stuff as long as I use a couple to stick the wood down flat.
They’re a lifesaver.