Run Ensemble8, open Alpha Media Player test, this warning occurs:
WARNING: CSS Error parsing jar:file:/Users/vadim/jfx/rt/apps/samples/Ensemble8/dist/Ensemble8.jar!/ensemble/samples/media/alphamediaplayer/AlphaMediaPlayer.css: expected series of <size> while parsing '-fx-background-image-slice' at [57,32]

Also happens in Overlay Media Player and Streaming Media Player