Not the OP, but I've built several ML pipelines in the last few years. Even if every step in the process very rigorous and using solid software, there are still

Not the OP, but I've built several ML pipelines in the last few years. Even if every step in the process very rigorous and using solid software, there are still challenges. ML models are very difficult (or impossible to test). The usual testing approaches don't work at all for ML features.