We're are aware of this issue and are working on a fix. We did, however, come up with a workaround in the meantime. Scannable only automatically processes business cards when you're signed into Evernote. If you scan a document (like a receipt or recipe) that is incorrectly identified as a business card, you can delete the scan (just swipe up in the tray for a quick delete), sign out of Evernote, and continue scanning. When you're finished, click the Save to Evernote button and log back in and the scan will be saved as document instead of a business card.
We realize this is cumbersome and apologize for the inconvenience!