My minecraft server isn't letting me in a certain spot?

So i started playing on play.dubcraft.net and went to creative. It let me in the first couple of times and then all of a sudden it said this.

Internal Exception: io.netty.handler.codec.DecoderException: com.google.gson.JsonSyntaxException:
com.google.gson.stream.MalformedJsonExc… Use JsonReader.setLenient(true) to accept malformed json at line 1 column 10

What does this mean and what do i got to do to fix it?

That's the server's fault. Only they can fix it.

Thats the server's error. If you wish to avoid these problems you can get your own minecraft server here.
]https://www.aim2game.com/clients/aff… You can see me and my friend using a server from them in the link below