I'd say you have multiple things going on that show up as random dark areas. #1. End grain on rails and styles were not sealed before staining. #2 A can of stain was dropped or otherwise splashed onto cabinet after they were stained but before they were clear coated (why it wasn't immediately wipped off is anyone's guess). #3. The dark scratch across doors is just that,something raked across doors leaving raised grain which absorbed excessive stain just like end grain. #4. And for good measure,there look's to be a few stray glue marks. Great looking solid Ash cabinets that are worth saving imo.