iOS app crashing after force quit, launch, lock, then unlock.

Hi,

I'm running into a strange bug with the iOS build of my application. On higher end devices with more memory the application shows a still shot of the previous session when the device is unlocked after a force quit, launch, lock, unlock sequence. This makes me think that the application is still using some amount of resources even after a force quit. On lower end devices with less memory the application shows the still shot and then crashes.

Is there a way to completely terminate an application on iOS. Or is this a known bug?

Thank you!