I broke it .... I broke my beloved Rokinon 12.
Was mountain biking, had a small Domke bungeed onto the bars, which is usually fine! It isn't mounted too rigidly, so the bag can sag and spring a little over bumps. Stopped to take more video, could NOT get it to focus, looked at the front of the lens and the entire core of it slid out into my hand. All the glass elements, in one plastic / metal housing, leaving a hollow amphitheater shaped housing with just the aperture mechanism back there.
I am so sad.