After going through a Nether Portal from either direction (from the Overworld or from the Nether), the game begins lagging periodically, giving a stop-go-stop-go effect. The effect continues with a high level of regularity (about once a second), and doesn't seem to stop until the player exits to the menu screen and then reloads the world, at which point the game continues to run normally.

Steps to Reproduce:
1. Go through a Nether Portal from either direction (Overworld or Nether). This may have to be repeated several times, since it doesn't consistently trigger the stop-go lag effect.

2. Exit to the menu and reload the game. The periodic lag should go away.