This issue only occurs on a server - not single player or playing via 'Open to LAN'.

I have three command blocks set up on a clock to display a /title for players in a specific area. When they enter this area (only on a server), it causes everyone online to be kicked with the following error message:

"Internal Exception: io.netty.handler.codec.DecoderException: com.google.son.JsonSyntaxException: com.google.son.stream.MalformedJsonException: Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 1"

Command blocks:
/title @a[996,211,1000,r=1] subtitle ["",

]
/title @a[996,211,1000,r=1] title []
/title @a[996,211,1000,r=1] times 0 3 2

Deleting the player data file allows me to sign back in to the server, since I respawn outside of that area, however the issue persists. Haven't yet tested in previous snapshots. Originally I thought having the command blocks set to 'Repeat' so rapidly might somehow be causing the issue, but it still happens even on a slow clock with 'Impulse' command blocks. Is affecting 3/3 of players who have tested it on their servers so far.

I can stop this by fixing the JSON of the second command to:
/title @a[996,211,1000,r=1] title ["",

]
However the kicking of the player for incorrect JSON seems a little odd, especially because it only occurs on multiplayer servers, no issues on single player.