On the server jar, randomly it will spam:
18.09 22:15:15 [Server] [Netty Epoll Server IO #12/ERROR io.netty.util.IllegalReferenceCountException: refCnt: 0

In console and then kick you from the server with:
Internal Exception: io.netty.handler.codec.DecoderException: java.lang.IndexOutOfBoundsException: readerInxex(13) + length(7251) exceeds writerIndex(13): UnpooledHeapByteBuf(ridx: 13, widx: 13, cap: 13)