Routing many prepares statements gives "#HY000Lost connection to backend server"

We have in production one max scale, routing and connection pooling queries between one web portal and a mysql server.

When running multiple prepare statements in parallell on the web-portal, maxscale closes the client connection with "#HY000Lost connection to backend server".
Tcpdump-ing the connections shows that the mysql-server replies correctly, but maxscale closes the client connection with "lost connection".
This causes the web-client session to fail.