For whatever reason ST hasn’t figured out how to use mobile presence APIs in Android. I have several other apps that use geofencing and have never had an issue with them. I am on a development team at work for mobile so I have used every Android phone under the sun for testing and the vasts majority of them are worthless as ST presence detectors.
The only one I have found that works is the Nexus 4, and it actually works phenomenally well. The Nexus 5 however is worthless as a mobile presence. The Galaxy S3 can also work but it seems to take several installations of the mobile presence for it to stick.
The standard reply from the ST Android team is the app can only work as well as the phone knows its own location. Well, every modern Android phone I have used is very good at knowing its location, and my heavy use of geofencing dependent apps proves that. Without fail when I pull into my work parking lot the rules on my device kick in to set the device to silent. The second I pull out it reverses that and turns the sound back up. Setting a reminder on Google Now to remember to get milk when I’m at HEB as another example also never fails.
SmartThings cannot continue to blame the phones for their inability to write a functional app. The above app that sets my phone to silent (Trigger) was developed by a college student. Tasker another app I use has had very dependable geofencing since before Android even had APIs for it.