In the desktop app, moving a card on the canvas left a few characters of the card highlighted after the drop. These clips are recorded in WebKit, the engine the app's window uses on macOS and Linux, with the same drag of the same card.
The card after the drop, close up: before, “ck” in “checkout” stays highlighted; after, nothing is.
The red dot is the mouse pointer. In Chrome (the browser version of Obeya) cards never selected their text, which is why the bug showed only in the app.