Preferred art selector not working as of 'Machine update
In the collection view you can see the arrows button to prompt to select preferred version/art, however clicking it just makes a click sound with no popup. Can't tell if it's only affecting the cards that gained new art from 'Machine, but there's also a bug affecting the choosing of card styles going back to recent updates (where some are just never visible, despite being owned in collection).
Additionally there's a more serious bug whereby the old cards now have the wrong set symbol (Machine instead of whatever set the old art comes from), which is horribly confusing.
All in all I think the way this is displayed in the interface should be via a toggle (option to display all owned versions of cards en masse as before the 'preferred art' function), because this would be a good fall back for situations like this.