I read over the following article, which advised that the first troubleshooting step to take is isolating the issue - which it sounds like you already did with your wife's iPhone. So, since we took care of that and determined it is isolated, according to the article you'll want to restore the iPhone to its factory condition. You can read more about it here:
Isolate the issue
Try to reproduce the issue with an identical or similar accessory, if one is available, or test with a second device.
Example: If you hear static coming from the left audio channel, try connecting a different device or try connecting to a different stereo or accessory that connects over the same interface (30-pin or Lightning connector, Bluetooth, or headphone jack).
Restore iPhone, iPad, or iPod touch
If you have isolated an issue to the device, restore iPhone, iPad, or iPod touch to its factory condition. You should rarely need to use this step with an accessory issue. If the issue affects only a third-party accessory, contact the accessory manufacturer before restoring your iOS device.
If the device does not update successfully, the issue may lie with the device and not with the accessory. See one of the following articles, depending on your device:
All the best,