Comment 7 for bug 1272463

I think you’re seeing another occurrence of bug #1240485: basically the UA override mechanism is inherently unreliable, and it sometimes will send the correct override, and sometimes not. That’s very unfortunate, and fixing that would require quite some work in QtWebKit itself. We’re investing in oxide at the moment, where this will be properly fixed.

Note that your proposed workaround, to have the webapp point to the non-secure domain, improves things because most of the times the UA override is correctly set before the redirection to the secure domain happens. It’s not a guarantee that it will work all the time though.