This is happening on Mac and PC.See attached FXML test case and screenshots.

The FXML has the following CSS applied which causes the issue:

.scroll-pane .viewport {
    -fx-background-color: transparent;
}

If you replace transparent with a solid color, the text inside the scrollPane renders as expected.

Use-case context, it is useful to make a ScrollPane completely transparent in order that it scrolls it's content over styling applied to an ancestor in the scenegraph.