Description: I played all three difficulties on Engage as well as on Focus to check this issue. Yes, it is happening on both. In the middle of the game, whoever needs to play, the opponent's card is displayed as white.
Cleared cache and started the app.
Clicked on Dev section and selected the Rob games
Under that, clicked on Hearts and selected the difficulty level as Hard.
Then started playing. After few minutes, opponent Patricia needed to play. The card appeared as white. Screenshot is attached.
This is kind of a rare bug so it may just be a matter of changing how the cards are loaded, code is attached with picture