A web printing system automatically detects the location of a wrinkle in a moving web. The web has a plurality of marked reference positions including an inboard position, a center position, and an outboard position. A plurality of contact image sensors detect the reference positions after the web passes through a spreader and an inboard distance and an outboard distance are respectively measured from the center position. If the inboard distance is less than a nominal inboard distance, the wrinkle is identified as inboard of the center position. If the outboard distance is less than a nominal outboard distance, the wrinkle is identified as outboard of the center position. The machine operator is notified of the fault condition and takes action to remedy the situation.