HCD.13:4.4 - Investigate apparent loss only when the distinction changes the next action

First check that the present demand is inside the earlier claim. Return an outside-envelope demand or known configuration failure directly.

When at least two live explanations would lead to different development or support work, and probing is safe and informative, use a qualified E.23.CAE differential. Recover a previously successful or separately qualified reference condition without further teaching. Vary the smallest condition that distinguishes the rivals. A reference–changed-condition–reference comparison can be useful when order or transition history matters.

Observe whether the person recognizes the applicable response, can access it, adapts it, enacts it and achieves the required result only where the evidence distinguishes those contributions. Do not infer every earlier failure from an incorrect final product.

If the response reappears without relearning under the qualified reference condition, a simple global-loss explanation is weakened in those conditions. That recovery does not prove unfamiliar transfer or identify a memory mechanism. If the probe teaches the answer, support changes cannot be separated, or safety prevents the contrast, return the unresolved distinction.

A warranted claim of changed capability requires holder-specific evidence after the relevant envelope and configuration rivals have been addressed. A single unsuccessful return probe is not enough by itself.