I am glad to see that you took some time to do your research before posting this question.
I have been doing a research and at this point, it would be better if you open a TAC case.
If the configuration is fine and you have confirmed that it only happens under certain circumstances then it could be a bug.
Please rate any helpful posts.
Did you find a solution to the problem? I have a very similar issue. While connected via AnyConnect or other sslvpn (Juniper), we are unable to connect to webex meetings. My next step is to open a tac case to see what they way.