The Eppley manoeuver is designed to reposition any of the calcium lumps (otoliths?) which may have detached from the sense hairs in the semi-cicular canals to the lowest of the three canals so that they may not overstimulate the balance hairs in the other canals. This is what produces the nausea and eye "flicking" when a sudden change in position of the head is made through 90 degrees. BPPV can happen without obvious cause and also tends to go away on it's own in time. I hope this helps you to make more sense of the condition?