I can't join a certain minecraft server without it showing this error:
Internal Exception: io.netty.handler.codec.DecoderException: java.lang.IndexOutOfBoundsException: readerIndex(51) + length(2) exceeds writerIndex(51): PooledUnsafeDirectByteBuf(ridx: 51, widx: 51, cap:51)
This is already fixed in 20w13b, see MC-175988.