Some of the problematic objects identified by our method. In most cases, if a track appears, it is closer to the object with respect to the aperture photometry, so it slightly affects the flux measurement. In the left column, one can see the image as identified by our algorithm, while in the right we report the light curve with the flagged epoch marked with red. The horizontal lines represent the threshold of the sigma clip. (See Figs. A.3 and A.4 for the whole sample.)