The upper planet shown has three fracture surfaces, all exactly spaced. Note the heavily smeared inner diameter on the left but absent on the opposite side of the fracture. This indicates roller rotation against a separated raceway. On the question of time, uncertain, but such conditions take more than a few seconds to develop. I would be interested in seeing the fracture propagation direction. If the planet were "squeezed " then fracture starts at ID at two places 180 degrees apart and OD opposite. The lower pictured pinion has one visible fracture likely starting at ID. If all fracture started at ID then it may be a gear vibratory resonance to get uniform 90 degrees away. Otherwise that's odd coincidence.