There was an overpopulation/underpopulation of mobs (e.g. too many Zephyrs, very little Aechor Plants, occasionally no Swets, etc.) This has been fixed, by scaling down the Zephyr spawn-rate a lot more.
Icestone used to freeze not only the source block but the stream also. When the source was frozen the stream would stay behind and doesn't go away. This has been fixed so that the source blocks are frozen instead, and the streams disappear afterwards.