I've been using the One SV for a few weeks and this has never happened before. Just trying to figure out if this is normal or is it a fault. I'm running the stock ROM ICS that came with the phone android 4.04, sense 4.1.

A few mins ago when I turned the phone on its side the home screen and everything flipped into landscape mode. It has never done that before except in an app or the browser. I have no other software or launcher/theme installed. The phone has been on its side many times and never flipped before on the home screen. Everything in the menus is now landscape. When I put the phone vertical it stays in landscape , despite me shaking the phone about. See screen shot of phone held vertically.

Has this happened to anyone else??

EDIT:
I've had to put into car mode then exit car mode to put it back to portrait. But when I plug it back onto charge with the USB or attach to the PC it flips right back to landscape.
I had the Desire HD go bonkers on me flipping into the location maps because of something before. I hope this isn't happening again the phone is brand new.