Man, I hate geofencing issues - they are a PITA to troubleshoot... So nothing changed on the application in regards to geofences, but (and this is a big one) the latest Google Play libraries which provide the enter/exit geofence events to the application was updated. I've been looking to put some more logging and viewing of the logs into the application, I might need to go ahead and do that for a beta this week.
Normally if a geofence fires and the action group cannot be executed it will show an execution notification -- do you get that at all? Might help determine if it is the fence or the sending of the action group. If no error, I suspect somehow the geofence boundary crossing is not reaching the app or I am not handling something correctly for the newest version of the services.