Worlds not loading, Browsing worlds through manage storage causes hang

Since 1.5.0 update (Aquatic update number 2) the following behavior is happening

Turtles and mobs freeze in groups and then move, Mining in creative mode has delayed smash effects. Tropical fish group together and exhbit same freeze - go - freeze behaviour.

80% of the time opening an existing world freezes, begins load then returns to the select world screen

Browsing storage - Manage storage - worlds causes device to hang for 2 - 4 minutes before displaying list.