There are problems with the application because it's possible the Battery Saver is turned on. While this feature is turned on, the Android system automatically puts applications to sleep to prevent battery drain. In some cases, Android analyses the power consumption and automatically puts applications into a hibernation state. This feature is available for Windows Phone and iOS as well. Of course, this could be a bug in the application. The Android apps are known to have all kind of bugs because of system updates, app updates, etc.
You can contact the developer of the application to communicate him this behavior at the following address: email@example.com