I finally caught my grain direction mistake after 4 crooked books, and a library sale tipped me off
Honestly I feel silly admitting this, but I was folding my signatures against the grain for about 2 months without noticing. I did 4 books back in March and all of them felt stiff when I opened them, like they wanted to snap shut on their own. Last Saturday I picked up a cheap paperback at a library sale in Tucson and ran my thumb along the spine edge, and it hit me that mine never felt like that. Turns out I was just grabbing paper out of the stack without checking which way the fibers run. Now I do the fold test on every sheet before I even score anything. Has anyone else messed this up, and do you mark your paper right when it comes in the door or test each sheet as you go?