React Native Upgrade -- 2

We have previous developer completed a React Native code upgrade for ios and Android to add the feature of geofence to our application, unfortunately from the beginning the upgrade causes the app to crash continually and the developer has not been able to resolve. The app is used for home automation system which also has voice skills. We require a specialized developer that understands current OS for ios and android using geofence feature to overcome the issues. There is also a need to add new features to the app which would be a separate scope.