Using numeric codes such as '0001' in the Names column of the Choices tab when creating a survey in Survey123 Connect interprets as an integer instead of a string, e.g. '1', in version 3.12 of both the Survey123 mobile and desktop app. This does not occur in the browser version or in previous versions of the mobile/desktop app.
This issue is not reproducible in ArcGIS Survey123. If the issue occurs, contact Esri Support Services as additional information is required for further investigation.