So, a while ago, my friend's server went down. No one can join, and when we try this error message shows up:

io.netty.handler.codec.DecoderException: java.lang.IndexOutOfBoundsException: readerIndex(31) + length(1) exceeds writerIndex(31): UnpooledHeapByteBuf(ridx: 31. widx: 31, cap:31)

I have no clue what is causing this, and no skill at all with java code, so if someone could please explain to me how to fix this without getting rid of the world created?