Recently, the screen on my iPhone stopped rotating when I moved the phone around. This happens in apps that do allow landscape orientation. Oddly, this only affects some apps, but not others. For example, I cannot use landscape orientation when I'm using iMessage, yet it works perfectly fine when I open the calendar. Just yesterday, I was able to use the landscape orientation for text messages, so I'm not sure what went wrong. The orientation lock is not on, and I've already tried closing all open apps. From the day I bought the iPhone, it always lagged when re-orienting the screen. Often times I would have to give the phone a minor "rattle" for it to register. Am I doing something wrong, or do I have a defective phone?