I have the same issue with a video node that is not shown.
I think the contrib is node-red-contrib-ui-media. Acts as a media player used to show pictures, video an audio. https://flows.nodered.org/node/node-red-contrib-ui-media (by gfcittolin on github).
The node load the video, and even you can preview it, but nothing is shown on dashboard. It seems that physical space is preserved but video does not appear.
The same on a Mac or Windows runs ok.
Tested with:
node-red 1.1.2
node-red-contrib-ui-media v1.2.0
Android 8.1.0
