If the dose was greater than 200mcg per day of selenium, then that could account for the negative side effects. Large amounts of MSM will cause various types of stomach aches too. Low doses are key in remaining comfortable. Higher doses cause symptoms and also cause deficiencies in other essential vitamins and minerals. Not good over time. They wouldn't have caused any stones to move.
Yoga helps increase circulation and massages the liver. This can bring on spontaneous flushes, but if that happened you would see some stones.