The latest version of the ArcGIS Collector 10.2.4 (Android version) is no longer respecting the presentation order of domain values. The web applications preseve the order as defined in the domain however the mobile collector app does not. There appears to be no logic to the order, its not alpha sorted, its not in the order the domains were created.
Can you share the service and map with me and I can take a look? You can share the service with Collector4ArcGIS. I tested a couple maps and the order matched iOS.