As Rumble Run is broken since last patch, I was looking to play on old adventures (Naxxramas, Black Mountains, League of Explorers, Karazhan).
And I was surprised to find a display bug in the Class Challenge of those adventures.
During the load of the Challenge menu, the background do not slide with the frame, and let the previous layer displayed as background.
This bug seems only affecting the portable version, I don’t have any issue on macOS.
https://us.forums.blizzard.com/en/hearthstone/t/display-bug-class-challenge-old-adventures/6955