SSL problem with self signed certificate

I have a customer running a LS server - exposed on the internet - but with a self-signed certificate. The certificate is not correctly signed for the domain at the moment but it expects WSS connections on port 9696.

If I go here in my browser: https://<hostname>:9696/monitor/
I am prompted by the browser to accept the incorrectly signed certificate and everything works fine.

However, my LS client code refuses to connect on the same hostname and port. I get an endless stream of errors in the Chrome console as it goes through its connect/fail/retry cycle
POST https://<hostname>:9696/lightstreamer/create_session.js net::ERR_INSECURE_RESPONSE lightstreamer.js?v=6.00:204l.pa lightstreamer.js?v=6.00:204e.bk lightstreamer.js?v=6.00:174q.fq lightstreamer.js?v=6.00:251q.Il lightstreamer.js?v=6.00:248q.Hb lightstreamer.js?v=6.00:247m.zd lightstreamer.js?v=6.00:190e lightstreamer.js?v=6.00:51a._callSuperMethod lightstreamer.js?v=6.00:52p.zd lightstreamer.js?v=6.00:256v.executeTask lightstreamer.js?v=6.00:49f

Why does the LS Javascript client behave differently to the monitor in this regard?

I had to kill the browser and start again - after that it accepted the connection from the LS client :)