Why do the subtle cases still slip past my screening?

You have gotten good at the obvious ones. You trust your screening now, and that trust is earned. But some cases arrive wearing an ordinary face, and only later do you see what was underneath. That gap is not carelessness. It is what ambiguity does — it hides, by definition, from a single pair of eyes. So stop asking for a sharper eye. You already have a good one; it is not the problem. What you lack is a rule that does not depend on noticing in the moment. No judgment, however trained, should be asked to catch what is built to be hard to read, alone, every time. Decide now, before the next case, what counts as unclear for you. Build the habit of stopping there, not pushing through on confidence. If a case ever touches someone's safety or wellbeing and you are unsure, do not wait — bring in a qualified professional right away.