JavaFX loads web page so slowly the Java application appears hung.
A web page ("visitor") containing JavaScript that allows a user to share their browser's view with another user ("agent") who is using a JavaFX-based browser.
The agent's viewing application appears to hang when the visitor's page has a background-color specified on a page with "iframe" that opens/closes. The specific background color is unimportant; it may be because the "flyout" background has opacity and this causes a problem when the main page has a background-color.