Created a new world based on a particular seed to use with latest snapshot, 16w02a. It plays just fine until I log out and then log back in. Immediately fall through the ground to below bedrock and game will not respond. Have tried it numerous times and it happens more often than not. I updated the world to 16w03a and it still happens. Tried same seed in 1.8 and didn't have problem.

However, log attached and it says that the world is open in another location. Would this error occur if I accidentally opened the world created in 16w02a in 1.8?

1. Play the world like normal.
2. Log out, save and exit.
3. Re-login, fall through world, unable to play.
4. Try to log in five or more times...fall through the world every time...except that one time when it decides to work and can continue to play...until logging out again and then logging back in, falling through world...repeat.