Force quit an app might be needed when using Pix4Dcapture to prevent any other apps from running in the background and creating a conflict, especially when connecting to the drone. Proceed as follows:
1. Open the Settings app of the Android device.
2. Scroll the list and tap Apps or Applications.
3. (optional) On certain devices like Samsung, tap Application Manager.
4. Scroll the list to find the app to force quit.
5. Tap FORCE STOP.