Expectation: no errors
Reality: Subject errors upon connecting to server.

To duplicate:
1. Have two instance of the SAME server.properties world (with same seed - server.properties attached) running on the same server (in different directories) but with the current dev build on port 25000 and version 1.8.8 on production port.

2. Logged into dev world with dev client.

3. Screenshot shows errors:

"runme.sh" 1L, 297C written
rgautier@rag-ubuntu:~/dev$ ./runme.sh
Java HotSpot(TM) Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release
Java HotSpot(TM) Server VM warning: Failed to reserve shared memory (errno = 22).
[10:35:43] [Server thread/INFO]: Starting minecraft server version 15w45a
[10:35:43] [Server thread/INFO]: Loading properties
[10:35:43] [Server thread/INFO]: Default game type: SURVIVAL
[10:35:43] [Server thread/INFO]: Generating keypair
[10:35:43] [Server thread/INFO]: Starting Minecraft server on *:25000
Java HotSpot(TM) Server VM warning: You have loaded library /tmp/libnetty-transport-native-epoll252295465381889224.so which might have disabled stack guard. The VM will try to fix the stack guard now.
It's highly recommended that you fix the library with 'execstack -c <libfile>', or link it with '-z noexecstack'.
[10:35:43] [Server thread/INFO]: Using default channel type
[10:35:43] [Server thread/INFO]: Preparing level "world"
[10:35:43] [Server thread/INFO]: Preparing start region for level 0
[10:35:44] [Server thread/INFO]: Preparing spawn area: 26%
[10:35:45] [Server thread/INFO]: Done (2.156s)! For help, type "help" or "?"
[10:37:32] User Authenticator #1/INFO: UUID of player RealFullpint is 99dd4c2a-9b86-4bf5-8d9f-0efdfbfe42f2
[10:37:33] [Server thread/INFO]: RealFullpint[/192.168.123.109:57301] logged in with entity id 317 at (-70.43658147421952, 67.0, 250.4708268521716)
[10:37:33] [Server thread/INFO]: RealFullpint joined the game
[10:37:33] [Server thread/WARN]: Tried to add entity Chicken with pending removal and duplicate UUID 8d5136be-3a6f-41e0-9fb6-d354565832cf
[10:37:33] [Server thread/WARN]: Tried to add entity Bat with pending removal and duplicate UUID bce5c2b5-93be-45cd-9f83-47fec92a2bdb
[10:37:33] [Server thread/WARN]: Tried to add entity Cow with pending removal and duplicate UUID bbf0cc0c-7591-44c5-aa98-44fb2b29f38a
[10:37:33] [Server thread/WARN]: Tried to add entity Creeper with pending removal and duplicate UUID 34979e84-bfa0-411a-8c49-0c06669f260c
[10:37:33] [Server thread/WARN]: Tried to add entity Creeper with pending removal and duplicate UUID e3da7d57-f808-40b2-97bc-99f7a851f3a6
[10:37:33] [Server thread/WARN]: Tried to add entity Zombie with pending removal and duplicate UUID 1596ea6c-0f28-43b5-9cd0-cd2ea196ed66
[10:37:33] [Server thread/WARN]: Tried to add entity Zombie with pending removal and duplicate UUID 303c1781-082b-4d74-abde-f3f529bc40f6
[10:37:33] [Server thread/WARN]: Tried to add entity Zombie with pending removal and duplicate UUID 12f19317-05d7-41f4-82a1-a2d1de66ca18
[10:37:33] [Server thread/WARN]: Tried to add entity Bat with pending removal and duplicate UUID 5164cb07-a3d8-4928-a922-024749d31da2
[10:37:33] [Server thread/WARN]: Tried to add entity Chicken with pending removal and duplicate UUID 4cf5de2a-1ffb-4cb0-8799-43ce31ee2efe
[10:37:33] [Server thread/WARN]: Tried to add entity Chicken with pending removal and duplicate UUID c2c6ac67-61ed-4b97-b982-dc487f293c2b
[10:37:33] [Server thread/WARN]: Tried to add entity Bat with pending removal and duplicate UUID b086da2f-9d8c-4874-bee3-f04dad63e56e
[10:37:33] [Server thread/WARN]: Tried to add entity Zombie with pending removal and duplicate UUID 6669c325-3c95-49f9-be31-db9bfb38b9b7
[10:40:32] [Server thread/INFO]: RealFullpint 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}}
[10:40:32] [Server thread/INFO]: RealFullpint left the game
[10:40:55] User Authenticator #2/INFO: UUID of player RealFullpint is 99dd4c2a-9b86-4bf5-8d9f-0efdfbfe42f2
[10:40:55] [Server thread/INFO]: RealFullpint[/192.168.123.109:58396] logged in with entity id 2147 at (-70.66845463293396, 67.0, 250.08272710275855)
[10:40:55] [Server thread/INFO]: RealFullpint joined the game
[10:41:14] [Server thread/INFO]: RealFullpint 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}}
[10:41:14] [Server thread/INFO]: RealFullpint left the game

Subsequent logins to the dev server did NOT replicate error.

Server.properties:

#Minecraft server properties
#Sat Nov 07 10:34:38 EST 2015
spawn-protection=16
max-tick-time=60000
generator-settings=
force-gamemode=false
allow-nether=true
gamemode=0
enable-query=false
player-idle-timeout=0
difficulty=1
spawn-monsters=true
op-permission-level=4
resource-pack-hash=
announce-player-achievements=true
pvp=true
snooper-enabled=true
level-type=DEFAULT
hardcore=false
enable-command-block=false
max-players=20
network-compression-threshold=256
max-world-size=29999984
server-port=25565
server-ip=
spawn-npcs=true
allow-flight=false
level-name=world
view-distance=7
resource-pack=
spawn-animals=true
white-list=false
generate-structures=true
online-mode=true
max-build-height=256
level-seed=4815162342
motd=Laughterland
enable-rcon=false

Runme.sh parameters to java (same for dev/production except jar name)

java -Xmn1G -Xss4M -Xmx2G -XX:+UseLargePages -XX:PermSize=256M -XX:+AggressiveOpts -XX:+UseFastAccessorMethods -XX:+UseStringCache -XX:+UseBiasedLocking -Xincgc -XX:MaxGCPauseMillis=10 -XX:SoftRefLRUPolicyMSPerMB=10000 -XX:+CMSParallelRemarkEnabled -XX:ParallelGCThreads=10 -Djava.net.preferIPv4Stack=true -jar minecraft_server.1.8.8.jar nogui