A data scientist has built a model that predicts demand for maintenance, and it looks good in the notebook. To put it into use, she sends the model file to IT, along with a document describing the columns it expects. IT rebuilds the input calculations, but does so slightly differently from the notebook. The model runs, but no one notices that its predictions are gradually drifting.
Later, someone from compliance asks which data the current version was trained on. No one can answer: the training table has been overwritten, the code is on a laptop, and no one knows which settings were used.
The problem is rarely the model itself. It is what is missing around it: a designated place for code, data and model versions, an automated route to production, and someone responsible once the model is running. MLOps helps you put that in place.