sometimes the head of a spectator looks solid

@unknown I might be able to attach the world, but it only appear when I've been in a certain area.
The screenshots are from my 15w47c version server, I could also give you the IP, because I don't know if any scoreboard value (un)assigned might effect it, so I can also guide you though, or even place signs to follow the steps in the effected world if I have to attach it

sorry for the music in the background, I was listening to it, and didn't realise it recorded it too.
as for the area I teleport to, it has a lot of redstone, if I return to the first area, the bug still occures

I didn't managed to reproduce the bug.
Can you attach a world save with the mentioned bug and the skins of the people involved ?

Are you using a resource pack, because in the video it looks like it but in the crash report the line is empty?

I might attach it later today.
I'll just put some signs down telling you what to do, because I don't know if any scoreboard values effect it
I was only capable of replicating it when on the server, alone, I'll have someone else check if it appears for him if he's alone too.

Also it happens regardless of resource pack

they see each other transparent
non spectators don't see the spectators
the only thing being touched by teams is that people with a OnlineTime 2880 score are joining a blue team and people with Moderator joining red
team rules edited away from default: color (blue/red) and seeFriendlyInvisibles (false)

still in 15w51b, even the hitbox still says it should have a hitbox.
if you can't reproduce this, I can give you a server IP which runs the exact map, so you can test it there

Confirmed for

• 15w51b

It just happend (randomly) for me. The player behaves partwise like not beeing in spectator mode: Flying through blocks zooms in and out the whole time.

Crash report (extract)

---- Minecraft Crash Report ----
// I just don't know what went wrong :(

Time: 22.12.15 15:31
Description: Manually triggered debug crash

java.lang.Throwable
	at bcb.aw(SourceFile:1675)
	at bcb.s(SourceFile:1596)
	at bcb.as(SourceFile:942)
	at bcb.a(SourceFile:386)
	at net.minecraft.client.main.Main.main(SourceFile:122)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
	at bcb.aw(SourceFile:1675)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bmi['Marcono1234'/472603, l='MpServer', x=173,57, y=82,05, z=964,81]]
	Chunk stats: MultiplayerChunkCache: 441, 441
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (225,64,253), Chunk: (at 1,4,13 in 14,15; contains blocks 224,0,240 to 239,255,255), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 19911 game time, 2378 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: Game mode: spectator (ID 3). Hardcore: false. Cheats: false
	Forced entities: 41 total; (This number might be incorrect as there were at least 200 ArmorStands)
	...

Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at bkj.a(SourceFile:364)
	at bcb.b(SourceFile:2496)
	at bcb.a(SourceFile:395)
	at net.minecraft.client.main.Main.main(SourceFile:122)

-- System Details --
Details:
	Minecraft Version: 15w51b
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.8.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 287526472 bytes (274 MB) / 665935872 bytes (635 MB) up to 1060372480 bytes (1011 MB)
	JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
	IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
	Launched Version: 15w51b
	LWJGL: 2.9.4
	OpenGL: AMD Radeon HD 6800 Series GL version 4.5.13399 Compatibility Profile Context 15.200.1062.1004, ATI Technologies Inc.
	GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

	Using VBOs: No
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: test (incompatible)
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	CPU: 6x AMD Phenom(tm) II X6 1055T Processor

I seem to have found a way to reproduce this, at least for me, the area in the video, going to spectator mode before the chunks correctly load makes it happen, can anybody confirm that?

resolving to MC-92916, this is not the only issue that arrives when teleporting to unloaded chunks