Turtle babies despawning

I have been waiting for this most recent update to fix the turtle breeding problem, but I’m frustrated because there seems to be a new problem.

I have been able to get the turtles to breed, lay eggs and the eggs hatch. But now I am experiencing turtle baby despawning. They have despawned in two ways.

In the first case, I was waiting for the turtle babies to mature so that I could harvest their scutes. I have my turtle farm on an island in an ocean biome, and I had traveled to the other side of the island to remove about 15 sections of wood fence, two or three chunks away, and when I came back the turtle babies were gone.

In the second case, I decided to stay with the turtle babies once they hatched so that they would not despawn. I was staying just a few blocks away from them, looking straight at them, when I quit the game. When I reloaded the world, the turtle babies were gone.

In addition to the turtle babies, I have noticed other despawning issues. Specifically, mobs such as cows and sheep, despawning from a leash attached to a post and despawning from a rowboat.