I've recently swapped my Z2, from a carrier locked; to one that's unlocked from Sony. Trouble is, the unlocked Z2 seems to be defective. The haptic feedback is super weak, to a point I can't tell if the motor is working. The thing is, if I perform a repeated action, such as tapping the back button (furiously), the vibration motor will then pick up momentum and start to vibrate properly. I've compared the two Z2, and the other Z2 (locked one) is performing as "expected".
So far, I've two areas/actions that are lacking in haptic feedback; typing on the stock keyboard (even though I've set the vibration duration to the default level), and the navbar buttons (back/home/recent) give a very very faint feedback.
I've ran several tests, including the ones from the service menu; and those worked wonderfully; the device would just vibrate right away. The device also has no problem vibrating when receiving phone calls or texts.
Just how many different vibration motors are in the phone? What could be causing weak haptic feedback?