Comment 3 for bug 1919033

Thanks, that seems reasonable; however, removing the line where the external mathjax is loaded does not resolve this issue.

I did some more testing: The epub file provided in the linked manual section works without problems. This seems to be since that epub only consists of a single html file. Once I add some div tags into its html source, which causes Calibre to split it into several html files upon conversion to epub, the bug starts to happen also here. You can try it yourself with the attached epub.

As I understand it the Calibre viewer reloads Mathjax every time it has to load a new html file, and if one tries to navigate in the viewer before the Mathjax is loaded this unhandled exception error is thrown. This occurs too often to make the viewer usable in my experience.