A bug in Apple's Journal app where undoing a deletion caused the entire sentence to disappear was highlighted. This severe issue, despite being found in a largely SwiftUI-based app, was actually within its UIKit text editing component. Such data-destroying bugs, particularly those affecting undo functionality, are typically considered critical and demand immediate attention in software engineering. Marcin Wichary emphasized that broken undo features should be prioritized for fixing over most other tasks. Apple PR confirmed that the Journal app's undo bug had been identified and a fix was in development. This fix has now been released in developer beta 2 for both macOS and iOS. However, the bug still exists in the current developer beta of macOS 26.6. Users are cautioned to be careful when writing in the Journal app due to this persistent issue. The original author had mistakenly attributed the bug to SwiftUI, but it was later clarified to be a UIKit problem. The fix indicates Apple's response to critical user experience flaws.