414m2 - I have never heard this before in my life.
However I do see a fall in performance in my cells if I leave them dumped for two weeks instead of my usual one week. If you just discharge to 5.4v and then store them they don't loose charge quickly. I store mine with low drain dischargers attached so within a week they will be fully dumped and equalized. I would never leave my nicd's charged when storing, I only ever store them discharged.
414m2 - I doubt your cells reversed, they probably needed a few cycles to come back to life, I see this with my nicd's if I don't use them for a few weeks.