The world is not being saved when I click "Save and Quit to Title"
Seems to only happen on a flat world I made, also does not happen 100% of the time.
Progress of buildings and commands entered into command blocks do not get saved, and/or are reset to how the world was the last time it was saved.
On the world I use, I go from survival to creative, and adventure mode.
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Please force a crash by pressing F3 + C for 10 seconds while in-game and attach the crash report ([minecraft|http://hopper.minecraft.net/help/finding-minecraft-data-folder]/crash-reports/crash-<DATE>-client.txt
) here.

Please attach the complete output of the "Development console" tab of the launcher.
Click the text, press CTRL-A to select all, then CTRL-C to copy, and CTRL-V to paste in a comment on this ticket.
If the launcher closes after game start, please edit your profile and select "Launcher visibility" then, "Keep the launcher open".
Refreshing local version list...
Launcher 1.2.5 (through bootstrap 5) started on windows...
Current time is Sep 28, 2013 10:50:05 PM
System.getProperty('os.name') == 'Windows 7'
System.getProperty('os.version') == '6.1'
System.getProperty('os.arch') == 'amd64'
System.getProperty('java.version') == '1.7.0_05'
System.getProperty('java.vendor') == 'Oracle Corporation'
System.getProperty('sun.arch.data.model') == '64'
Refreshing remote version list...
Refresh complete.
Loaded 3 profile(s); selected 'Snapshot'
Refreshing auth...
Logging in with access token
Delta time to compare resources: 1274 ms
Download job 'Resources' skipped as there are no files to download
Job 'Resources' finished successfully
Getting syncinfo for selected version
Queueing library & version downloads
Download job 'Version & Libraries' started (8 threads, 24 files)
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\paulscode\soundsystem\20120107\soundsystem-20120107.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\net\java\jutils\jutils\1.0.0\jutils-1.0.0.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\org\apache\logging\log4j\log4j-api\2.0-beta9\log4j-api-2.0-beta9.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\net\sf\jopt-simple\jopt-simple\4.5\jopt-simple-4.5.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\org\apache\commons\commons-lang3\3.1\commons-lang3-3.1.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\org\lwjgl\lwjgl\lwjgl_util\2.9.0\lwjgl_util-2.9.0.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\java3d\vecmath\1.3.1\vecmath-1.3.1.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\mojang\authlib\1.1\authlib-1.1.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\google\guava\guava\14.0\guava-14.0.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\net\sf\trove4j\trove4j\3.0.3\trove4j-3.0.3.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\ibm\icu\icu4j-core-mojang\51.2\icu4j-core-mojang-51.2.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\paulscode\libraryjavasound\20101123\libraryjavasound-20101123.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\paulscode\codecwav\20101023\codecwav-20101023.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\google\code\gson\gson\2.2.2\gson-2.2.2.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\org\lwjgl\lwjgl\lwjgl-platform\2.9.0\lwjgl-platform-2.9.0-natives-windows.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\net\java\jinput\jinput-platform\2.0.5\jinput-platform-2.0.5-natives-windows.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\net\java\jinput\jinput\2.0.5\jinput-2.0.5.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\paulscode\librarylwjglopenal\20100824\librarylwjglopenal-20100824.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\paulscode\codecjorbis\20101023\codecjorbis-20101023.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\org\lwjgl\lwjgl\lwjgl\2.9.0\lwjgl-2.9.0.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\org\apache\logging\log4j\log4j-core\2.0-beta9\log4j-core-2.0-beta9.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\commons-io\commons-io\2.4\commons-io-2.4.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\org\bouncycastle\bcprov-jdk15on\1.47\bcprov-jdk15on-1.47.jar for job 'Version & Libraries': Used own copy as it matched etag
Finished downloading C:\Users\Ethan\AppData\Roaming\.minecraft\versions\13w39b\13w39b.jar for job 'Version & Libraries': Used own copy as it matched etag
Job 'Version & Libraries' finished successfully
Launching game
Looking for old natives to clean up...
Unpacking natives to C:\Users\Ethan\AppData\Roaming\.minecraft\versions\13w39b\13w39b-natives-32180904636455
Launching in C:\Users\Ethan\AppData\Roaming\.minecraft
Running C:\Program Files\Java\jre7\bin\javaw.exe -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -Djava.library.path=C:\Users\Ethan\AppData\Roaming\.minecraft\versions\13w39b\13w39b-natives-32180904636455 -cp C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\java3d\vecmath\1.3.1\vecmath-1.3.1.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\net\sf\trove4j\trove4j\3.0.3\trove4j-3.0.3.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\ibm\icu\icu4j-core-mojang\51.2\icu4j-core-mojang-51.2.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\net\sf\jopt-simple\jopt-simple\4.5\jopt-simple-4.5.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\paulscode\codecjorbis\20101023\codecjorbis-20101023.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\paulscode\codecwav\20101023\codecwav-20101023.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\paulscode\libraryjavasound\20101123\libraryjavasound-20101123.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\paulscode\librarylwjglopenal\20100824\librarylwjglopenal-20100824.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\paulscode\soundsystem\20120107\soundsystem-20120107.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\org\bouncycastle\bcprov-jdk15on\1.47\bcprov-jdk15on-1.47.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\google\guava\guava\14.0\guava-14.0.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\org\apache\commons\commons-lang3\3.1\commons-lang3-3.1.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\commons-io\commons-io\2.4\commons-io-2.4.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\net\java\jinput\jinput\2.0.5\jinput-2.0.5.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\net\java\jutils\jutils\1.0.0\jutils-1.0.0.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\google\code\gson\gson\2.2.2\gson-2.2.2.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\com\mojang\authlib\1.1\authlib-1.1.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\org\apache\logging\log4j\log4j-api\2.0-beta9\log4j-api-2.0-beta9.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\org\apache\logging\log4j\log4j-core\2.0-beta9\log4j-core-2.0-beta9.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\org\lwjgl\lwjgl\lwjgl\2.9.0\lwjgl-2.9.0.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\libraries\org\lwjgl\lwjgl\lwjgl_util\2.9.0\lwjgl_util-2.9.0.jar;C:\Users\Ethan\AppData\Roaming\.minecraft\versions\13w39b\13w39b.jar net.minecraft.client.main.Main --username Charnuz --session token:c6e3ca8b731c49d0a4336ded74b144e3:bdc8545a80a1416bb6f7958591fbf399 --version 13w39b --gameDir C:\Users\Ethan\AppData\Roaming\.minecraft --assetsDir C:\Users\Ethan\AppData\Roaming\.minecraft\assets --uuid bdc8545a80a1416bb6f7958591fbf399 --accessToken c6e3ca8b731c49d0a4336ded74b144e3
Client>
Client> Starting up SoundSystem...
Client> Initializing LWJGL OpenAL
Client> (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
Client> OpenAL initialized.
Client>
Client> 22:51:46.219 [Server Listen Thread] ERROR jt - Exception handling pending connection
Client> java.net.SocketException: socket closed
Client> at java.net.TwoStacksPlainSocketImpl.socketAccept(Native Method) ~[?:1.7.0_05]
Client> at java.net.AbstractPlainSocketImpl.accept(Unknown Source) ~[?:1.7.0_05]
Client> at java.net.PlainSocketImpl.accept(Unknown Source) ~[?:1.7.0_05]
Client> at java.net.ServerSocket.implAccept(Unknown Source) ~[?:1.7.0_05]
Client> at java.net.ServerSocket.accept(Unknown Source) ~[?:1.7.0_05]
Client> at jt.run(SourceFile:66) [13w39b.jar:?]
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I am not sure if this is exactly what you wanted, but I hope so. 😛

Yes, that was it, but because of MC-32762 the interesting part of the console log is missing.
Wait for the next snapshot (where hopefully the logging is fixed) and post a new console log if the issue is still persisting.