Yeah had this soon after getting it. Neither Vodafone nor Apple were interested, the most common symptom is the touchscreen becomes unresponsive with a grey flickering bar at the top.
The problem is not the phone becoming warped in itself, most phones of any make and model bend a little. Apple were forced to admit earlier this month that the solder used in the 6 Plus models was cheap and nasty, and very fragile to developing cracks under normal use. The very slightest of flex can break the poor quality solder they used during manufacture.
I have had to live with infuriating issue for over a year. It's a manufacturing fault and Apple are 100% liable for repair/replacement costs.
