The javafx.fxml module uses two classes from the sun.reflect package:

sun.reflect.CallerSensitive
sun.reflect.Reflection

With JDK-8137058 most classes in the sun.reflect package are moving to the jdk.internal.reflect package, including those two. We either need to find an alternative using public API or react to the move prior to JDK-8137058 going into 9-dev.