Hi, did you guys encountered freezed screen on your iPhone 6s / 6s plus?

Mine would occasionally freeze when I picked up a call while inside WhatsApp / Facebook. Means, the screen won't respond to touch after I end the call. I can still see my screen before the call, and I need to screen off, then it will be normal again when I wake the device again

I'm on iOS 9.2.1, 6s plus. My phone have a glass protector on it, no cracks / hair / dust stuck in the screen area.