Kicked from server, Console spams "Netty Epoll Server IO #6/ERROR"

When playing on a server running the affected version, the server can only handle 1 player online at the time.

Other players connecting get kicked out after 2/3 seconds with the following message in the server console.

Netty Epoll Server IO #6/ERROR io.netty.util.IllegalReferenceCountException: refCnt: 0

and the players get the message;

Internal Exception: io.netty.handler.codec.DecoderException: java.lang.IndexOutOfBoundsException: readerIndix(17) + length(58090) exceeds writerIndex(17); UnpooledHeapyByteBuf(ridx: 17, widx: 17, cap: 17)

The first player on the server has no problems playing. But if he/she is second, he/she will get kicked out.