Finding
Location, posture, fatigue, background noise, reach, device availability and the people normally present can change whether the same configuration produces the intended outcome.
How the mechanism works
The environment changes the demands placed on the operator. A configuration that succeeds at a desk or during a demonstration may fail from the person’s usual position or later in the day.
Evidence boundary
Observing functional variation does not establish a clinical cause. Record what was observed and tested without diagnosing beyond the evidence.