Hi Again,
I just updated to 1.8 and made a world on CUSTOMIZED setting. It functions perfectly during game play, but crashes while attempting to save the world. I'm not sure if this will help -
[22:09:14] [Client thread/INFO]: Setting user: GroundHound101
[22:09:16] [Client thread/INFO]: LWJGL Version: 2.9.1
[22:09:16] [Client thread/INFO]: Reloading ResourceManager: Default, Sanity.zip
[22:09:17] [Sound Library Loader/INFO]: Starting up SoundSystem...
[22:09:17] [Client thread/WARN]: File minecraft:sounds/mob/ghast/fireball.ogg does not exist, cannot add it to event minecraft:item.fireCharge.use
[22:09:17] [Thread-6/INFO]: Initializing LWJGL OpenAL
[22:09:17] [Thread-6/INFO]: (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
[22:09:17] [Thread-6/INFO]: OpenAL initialized.
[22:09:18] [Sound Library Loader/INFO]: Sound engine started
[22:09:19] [Client thread/WARN]: Texture minecraft:textures/items/lead.png with size 15x15 limits mip level from 4 to 0
[22:09:19] [Client thread/INFO]: Created: 512x512 textures-atlas
[22:09:28] [Client thread/ERROR]: Can't ping Hivemc.eu: Disconnected
[22:09:29] [Client thread/ERROR]: Can't ping The-reef.EU: Disconnected
[22:09:29] [Client thread/ERROR]: Can't ping Woodycraft.net: Disconnected
[22:09:30] [Client thread/ERROR]: Can't ping play.cubecraftgames.net: Disconnected
[22:09:40] [Client thread/ERROR]: Can't ping Woodycraft.net: Disconnected
[22:09:40] [Client thread/ERROR]: Can't ping play.cubecraftgames.net: Disconnected
[22:09:41] [Client thread/ERROR]: Can't ping Hivemc.eu: Disconnected
[22:09:42] [Client thread/ERROR]: Can't ping The-reef.EU: Disconnected
[22:10:08] [Client thread/ERROR]: Can't ping The-reef.EU: Disconnected
[22:10:09] [Client thread/ERROR]: Can't ping Woodycraft.net: Disconnected
[22:10:09] [Client thread/ERROR]: Can't ping play.cubecraftgames.net: Disconnected
[22:10:09] [Client thread/ERROR]: Can't ping Hivemc.eu: Disconnected
[22:12:54] [Server thread/INFO]: Starting integrated minecraft server version 1.8
[22:12:54] [Server thread/INFO]: Generating keypair
[22:12:55] [Server thread/INFO]: Preparing start region for level 0
[22:12:56] [Server thread/INFO]: Preparing spawn area: 77%
[22:12:56] [Server thread/INFO]: GroundHound101[local:E:67cebc17] logged in with entity id 299 at (-310.8787485535104, 70.0, 266.4317168381474)
[22:12:56] [Server thread/INFO]: GroundHound101 joined the game
[22:12:56] [Server thread/INFO]: Changing view distance to 21, from 10
[22:12:58] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 2433ms behind, skipping 48 tick(s)
[22:12:58] [Server thread/INFO]: Saving and pausing game...
[22:12:58] [Server thread/INFO]: Saving chunks for level 'First 1.8'/Overworld
[22:12:59] [Server thread/INFO]: Saving chunks for level 'First 1.8'/Nether
[22:12:59] [Server thread/INFO]: Saving chunks for level 'First 1.8'/The End
[22:13:01] [Client thread/INFO]: Started on 56041
[22:13:01] [Client thread/INFO]: [CHAT] Local game hosted on port 56041
[22:13:05] [Server thread/INFO]: GroundHound101 lost connection: TextComponent{text='Disconnected', siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null, insertion=null}}
[22:13:05] [Server thread/INFO]: GroundHound101 left the game
[22:13:05] [Server thread/INFO]: Stopping singleplayer server as player logged out
[22:13:05] [Server thread/INFO]: Stopping server
[22:13:05] [Server thread/INFO]: Saving players
[22:13:05] [Server thread/INFO]: Saving worlds
[22:13:05] [Server thread/INFO]: Saving chunks for level 'First 1.8'/Overworld
[22:13:05] [Server thread/INFO]: Saving chunks for level 'First 1.8'/Nether
[22:13:05] [Server thread/INFO]: Saving chunks for level 'First 1.8'/The End
Linked issues
is duplicated by 6
Attachments
Comments 26

I waited for 10 minutes, my computer constantly reminding me that the program has become unresponsive.

Please do the following:
Recreate the situation by leaving the game
Navigate to
.minecraft/saves/<WORLDNAME>/region/
and observe by spamming F5 if the files are changing the access date and the file size is increasing
I can confirm this happening to me sometimes, even on newly created and untouched superflat worlds, which should have almost nothing to save.
So far this only seems to happen to me when flying in creative. Specifically when I press ESC while moving and press Save and Quit while the character is still gliding.
Edit: Which is also to say as long as I always make sure my feet are on the ground in my local LAN game it doesn't freeze on quit.

Reproduced this today in modded 1.8.9. Normally I know you don't care about modded, but I did manage to use WhatIsHang to get some info: https://gist.github.com/Pokechu22/f58001b188e1062d97b0adc6e4f6a550. I don't know how useful this is, but I think it may be at least somewhat helpful. (And yes, my modded install is really wonky - blame old mod management scripts of mine).

Reproduced in 1.10, but I did have optifine installed. This time I ran jstack
; here's the result: https://gist.github.com/Pokechu22/4db37a3a4e432bfedeffa3da8f9a4b21. Note that optifine did mess with some of the classes in that stacktrace (you can tell because of the non-obfuscated source file), which is unfortunate, but this should hopefully give some information that may be moderately useful.

Is this still an issue in the most recent versions (currently that is 1.10.2, or 16w43a) of Minecraft? If so, please update the affected versions and help us keeping this ticket updated from time to time. If you are the owner/reporter of this ticket, you can modify the affected version(s) yourself.

Duplicate of MC-72943 (it's been specified that this only happens when open to lan is used).

Resolving as duplicate of MC-72943 since the original game output log of this ticket mentions a LAN game:
[CHAT] Local game hosted on port 56041
Cannot see a crash.
How long did you wait ?
Customized worlds may take some minutes until being saved (chunks are still generated and saved at the same time)