Apparatuses and methods for detecting failures in a photoreactive 3D printing system include a light-emitting device configured to emit light into and along a plane of a membrane or of a substrate below the membrane. The membrane is a bottom surface of a resin tub. The light has a wavelength that is different from a photopolymerization wavelength of resin in the resin tub. The membrane or substrate is transparent to the wavelength of the light and to the photopolymerization wavelength. An imaging device is oriented to capture an image of the light emitted from the membrane or the substrate. A detection system is in communication with the imaging device, the detection system being configured to detect a spatial or temporal disruption in the image.