Have you ever had what was seemingly a good piece of lumber turn out to be a miserable you know what? I had a rough cut 5/4 Cherry board, 7 1/2" wide by 6' long that was at least 15 years old that I cut up into 18 inch lengths for a project I wanted to get started. There was some twist but nothing to write home about and there was some cupping. No matter what I did, I couldn't get those 18" pieces flat to save my life. I'm normally good at flattening boards with hand planes, jointer, drum sander etc. but today was just not my day. I've flattened 100's of boards without too many issues over the years but after 3 plus hours, I took all those pieces and decided I would get my revenge next spring at our first camp fire. I'm assuming there was a lot of internal stress that just wouldn't relax. Sometimes you just have to give up on a piece of wood and move on to the next board. Thankfully that board was given to me so I lost nothing other than my time and patience! Ok, now that I've vented, I feel better!