We strive to create quality software and learning from mistakes can help us avoid similar issues.This also helps encourage a 'testing can be fun' mindset.
Penalizing your development team for bugs is penny wise and pound foolish. Focus on practices that promote quality and embrace bugs as part of the process.
The bug appeared when testing on iOS 7 but not iOS 8, which suggested the root cause might be a floating point error with the constraint layout library.
