In your case, there would be an overlap. A digital interface is UI. UX is multi disciplinary, it would focus more on the human centered process of building an application that fits the user needs. Ergonomic specialists would take into account the job (task), physical environment, user need, equipement (does the worker wear gloves...). Some are trained to be able to work on both fields (Human factor, cognitive engineer...)

UX could also be called cognitive ergonomics.