http://www.spigotmc.org/threads/invisible-bug.63281/

I've had this happen quite a lot. The fix that I used was to not allow a player to join if they have a client already online, and if that happened, kick both clients.

@Jannik8500 no, I had this issue in 1.8.* but it's working fine in 1.9.* for me.

@comonier Spigot 1.8.x is no longer supported.

@everyone: Is this issue in 1.9 also?

hello.... i also use spigot 1.8.8
and this issue begins after a make last version authme update...
dont know if its true... but have same problem here.

the hacky fix that I implemented was to not allow a disconnect then a new join from the same player within 5 seconds. The teleport invisibility bug and this bug are completely different I think. This only occurs when they disconnect and reconnect in the same instant, hence the "logged in from another location" showing in the logs

Did not fixed it btw.

Holy cow, I do teleport them to spawn indeed.. Can you please add me on skype and help me further? (Chris_GSPvP is my skype).

@Chris for me this appeared on teleport, not login. Are you teleporting players after login? If so, try to stagger the teleport packets, and do the hide/show.

Already tried.....

Not sure about the entire issue, but noting that it's a client issue, perhaps you should wait longer than 5 ticks...

Yes, on join after 5 ticks I first hide them and then unhide them, didn't worked.

Did you try hiding and unhiding players on join?

No RoboMWM, this is not true. I tried that workaround and it didn't fixed it.

Guys, refer to Dylan Katz' comment, for both information about the problem and a temporary workaround.

Even still, I've had issues with this on vanilla servers as well as Forge based mod packs, I think this needs patching up inside the Minecraft Server/Client itself and not in Bukkit/Spigot.
There are a huge number of tickets against Mojang regarding entities and other issues with items suffering from invisibility.

no, this is definitely server related, it only happens when you have the double login as shown in my other comment

You're looking in the wrong area, this is not a Spigot/bukkit bug but a bug in Minecraft client itself.

Still no fix for this?

Bungee logs from one of the occurrences that this happens on my server maybe will help

23:21:37 [INFO] [Auty7373] <-> ServerConnector [spleef] has connected
23:21:37 [INFO] [Auty7373] disconnected with: ?cYou are already connected to this server!
23:21:37 [INFO] [Auty7373] disconnected with: ?cYou are already connected to this server!
23:21:37 [INFO] [Auty7373] <-> ServerConnector [spleef] has connected
23:21:37 [INFO] [Auty7373] disconnected with: ?fYou logged in from another location
23:21:37 [INFO] [Auty7373] <> DownstreamBridge <> [spleef] has disconnected

I've been getting the same issue on spigot 1.8.4, without the "Logged in from another location" message. This is an issue in the Minecraft client, and is covered in the Mojang bug trackers with this bug, and seems to be caused by this bug. My workaround for this is hiding then showing players after rapid teleport, which is when this bug occurred for me.

Has this been tried on a vanilla server?
I also seem to recognize this type of bug inside a few modded servers too, sometimes a player will join and be invisible

Your build is not the latest and therefore may be the reason you are having this issue. Spigot is 1 version(s) behind. CraftBukkit is 1 version(s) behind. This message was automatically generated and is not guaranteed to be a solution to your issue.