JavaFX 13 Webview hangs

[Lior Yaffe]

My application is a Java application running a Javascript/Html website
inside a JavaFX WebView. It was working stable for several years with
various versions of Java and JavaFX.
As far as I can tell it is following best coding practices such as running
all UI code in the JavaFX thread and as such.

Since upgrading to JavaFX 13 my application hangs sporadically. When it
happens the website running inside the webview becomes unresponsive and
displays an hourglass icon.
When the app hangs I cannot take a thread dump using jstack or close the
application. I have to kill it.

The problem is reproduced on multiple Windows workstations. It was never
reported or reproduced on Linux or Mac so there is a chance it is Windows
specific.
When the app hangs the CPU is ideal so this is not a busy loop.
Which diagnostic information can I obtain to better understand this problem?