> Not sure what you mean by "scene graph".
See the following articles to see what the scene graph is:
*
https://docs.oracle.com/javafx/2/architecture/jfxpub-architecture.htm#A1106328
*
https://docs.oracle.com/javafx/2/scenegraph/jfxpub-scenegraph.htm
Basically, if a node is in an active scene graph, i.e. attached to a displayed window or a scene you try to snapshot, then you can't set or query any of the properties of any the node which is attached to the scene graph, or change the structure of the scene graph by adding or removing nodes.
> Is there a way where we can do something wrong in this area and not see it right away?
Yes, when you modify or query a value off of the JavaFX application thread, then there is no guarantee that an exception will be thrown which you can handle, indeed it may just break the app in an unpredictable way due to a phenomenon known as a race condition:
https://en.wikipedia.org/wiki/Race_condition#Example
Sometimes the JavaFX system is sophisticated enough to detect some sources of potential race conditions and raise exceptions before they occur, other times it is not, and some unexpected error just occurs.
I couldn't tell you if you have a race condition in your code, but it is one possible cause of exceptions like the one you logged. In my experience, unless there is a coding error in the underlying JavaFX framework, a race condition is the most likely cause of issues similar to what you are observing.
One reason why I asked if the stack trace is always the same, is that sometimes when you have a race condition, an error can manifest itself in different ways, seeming somewhat random and the exact location where the exception occurs can change depending upon when data was concurrently modified or viewed by different threads.
> Javafx.runtime.version=8.0.112
If the problem is actually an internal error in JavaFX, and not in your code, then you could try upgrading to a later version of JavaFX and seeing if it fixes the issue (because a bug fix which occurred sometime in the last few years might have fixed the cause of the issue).