Turtle AI broken

Turtles will no longer move unless I am holding sea grass. They will remain motionless either on land or in water. This was on an old world of mine that had been updated. I  created a new world and spawned in a few turtles – these moved for a few seconds and then became still. If they are bred using sea grass they do make eggs, but then sit still again. I did not wait to see what the babies would do.