[MC-41327] Client Crashes in certain new areas in SMP

In certain areas client crashes with msg 'internal server error'
Server stays up, other players unaffected if on.
Upon reconnection the same error occurs.
I have pasted the output on the server side at the bottom.
Other players seem to be able to walk around in the affected areas OK

The only way I have been able to connect again is to copy the player.dat to my local machine, edit the POS field to a known OK location and copy it back. I can then play again until I walk to a location that has the issue.

It always seems to be new locations, never somewhere i have been before.

I have tried deleting my AppData\Roaming\.minecraft directory and re-downloading, the issue still occurs, and at the same locations.

Also
/tp ing to known affected areas makes player appear in the void, and die with the msg 'player fell out of the world'. I am no near the edge of the world. When this happens server crashes.
(i have not been able to get other players to test this sorry)

creating a portal in the nether that comes out at a known trouble location also causes a server crash, I have attached a crash report from this happening today. I have not been able to get other players to test walking through this portal yet either sorry.

Here is the output on the server side from it occurring today -
You can see when it occurs, and when I try and reconnect.

[17:27:18] [Server thread/WARN]: Failed to handle packet for /XXX.XXX.XXX.XXX:YYYYY
java.lang.NullPointerException
        at atp.a(SourceFile:86) ~[minecraft_server.jar:?]
        at apl.a(SourceFile:403) ~[minecraft_server.jar:?]
        at mi.a(SourceFile:160) ~[minecraft_server.jar:?]
        at aoj.a(SourceFile:775) ~[minecraft_server.jar:?]
        at mi.c(SourceFile:95) ~[minecraft_server.jar:?]
        at mh.<init>(SourceFile:31) ~[minecraft_server.jar:?]
        at mg.a(SourceFile:212) ~[minecraft_server.jar:?]
        at mg.d(SourceFile:346) ~[minecraft_server.jar:?]
        at ld.d(SourceFile:215) ~[minecraft_server.jar:?]
        at mx.a(SourceFile:280) ~[minecraft_server.jar:?]
        at ir.a(SourceFile:137) ~[minecraft_server.jar:?]
        at it.a(SourceFile:20) ~[minecraft_server.jar:?]
        at ef.a(SourceFile:164) ~[minecraft_server.jar:?]
        at ms.c(SourceFile:134) [minecraft_server.jar:?]
        at net.minecraft.server.MinecraftServer.u(SourceFile:529) [minecraft_server.jar:?]
        at lj.u(SourceFile:265) [minecraft_server.jar:?]
        at net.minecraft.server.MinecraftServer.t(SourceFile:441) [minecraft_server.jar:?]
        at net.minecraft.server.MinecraftServer.run(SourceFile:358) [minecraft_server.jar:?]
        at ky.run(SourceFile:617) [minecraft_server.jar:?]
[17:27:18] [Server thread/INFO]: stewbags lost connection: TextComponent{text='Internal server error', siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null}}
[17:27:18] [Server thread/INFO]: stewbags left the game
[17:28:05] [User Authenticator #2/INFO]: UUID of player stewbags is 793e6cc51613411899f010732bc2960b
[17:28:05] [Server thread/INFO]: stewbags/XXX.XXX.XXX.XXX:YYYYY] logged in with entity id 43666 at (-5318.641780164287, 81.00133597911214, -2817.041827964927)
[17:28:05] [Server thread/INFO]: stewbags joined the game
[17:28:07] [Server thread/WARN]: Failed to handle packet for /XXX.XXX.XXX.XXX:YYYYY
java.lang.NullPointerException
        at atp.a(SourceFile:86) ~[minecraft_server.jar:?]
        at apl.a(SourceFile:403) ~[minecraft_server.jar:?]
        at mi.a(SourceFile:160) ~[minecraft_server.jar:?]
        at aoj.a(SourceFile:781) ~[minecraft_server.jar:?]
        at mi.c(SourceFile:95) ~[minecraft_server.jar:?]
        at mh.<init>(SourceFile:31) ~[minecraft_server.jar:?]
        at mg.a(SourceFile:212) ~[minecraft_server.jar:?]
        at mg.a(SourceFile:249) ~[minecraft_server.jar:?]
        at ld.a(SourceFile:155) ~[minecraft_server.jar:?]
        at ld.c(SourceFile:206) ~[minecraft_server.jar:?]
        at ld.a(SourceFile:100) ~[minecraft_server.jar:?]
        at nd.c(SourceFile:87) ~[minecraft_server.jar:?]
        at nd.a(SourceFile:52) ~[minecraft_server.jar:?]
        at ef.a(SourceFile:166) ~[minecraft_server.jar:?]
        at ms.c(SourceFile:134) [minecraft_server.jar:?]
        at net.minecraft.server.MinecraftServer.u(SourceFile:529) [minecraft_server.jar:?]
        at lj.u(SourceFile:265) [minecraft_server.jar:?]
        at net.minecraft.server.MinecraftServer.t(SourceFile:441) [minecraft_server.jar:?]
        at net.minecraft.server.MinecraftServer.run(SourceFile:358) [minecraft_server.jar:?]
        at ky.run(SourceFile:617) [minecraft_server.jar:?]
[17:28:07] [Server thread/INFO]: stewbags lost connection: TextComponent{text='Internal server error', siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null}}
[17:28:07] [Server thread/INFO]: stewbags left the game