If you can get log output from the client (adb logcat), that would also help, but they may not have the technical ability to do so.
Keep in mind that unless you're using Crosswalk, the system web view that your app receives will be different on every OS version and manufacturer device. That might be part of your problem there, so I'd encourage you to try the Crosswalk plugin.
Lastly, what version of PhoneGap are you using to build the app? What version of cordova-android is installed in your app? Are you using PhoneGap Build or the CLI?