There are two annotation classes in buildSrc that cannot be seen in a jigsaw enabled build. These are:

buildSrc/src/main/java/com/sun/javafx/beans/annotations/Default.java
buildSrc/src/main/java/com/sun/javafx/collections/annotations/ReturnsUnmodifiableCollection.java

The current workaround/solution is to copy these files into the base module and add the following exports

    exports com.sun.javafx.beans.annotations to
        javafx.controls,
        javafx.graphics;
    exports com.sun.javafx.collections.annotations to
        javafx.controls,
        javafx.graphics;