Re: Certificate chain
"If there's a problem with the certificate chain how come only Firefox is complaining about it and not all browsers?"
Because every browser is different. Even different Chromium based browsers are different than Chrome itself.
Firefox is a very different beast than Chrome or from Safari. Firefox complains more about things like broken certificate chains vs. Chrome. Chrome complains different things like requiring SAN entries instead of depending on cn= in the X.509 cert.
Thus if you run a web app, best to check it in all the major browsers..