How do you know when an automated workflow is doing more harm than good?

We built an automated setup to cut down on repetitive team tasks and speed things up. It handled basic cases fast, but the moment tiny exceptions popped up, it broke or got things wrong.

Instead of saving hours, our team now spends that time reviewing and fixing the automated outputs. It didn't solve the workload, it just moved the effort to a different step.

What rules do you follow to decide which processes stay manual versus which ones get automated?