Help Everything Minimises on Screen Lock

[geoff-r]

Hi there, this is my first post on here. I've been lurking on the forum for some time and it has been a huge help! Anyway my phone has recently started playing up. If I have anything open, for example a text message, or a picture, literally anything, and the screen locks after 30 seconds, I go to unlock it and whatever I was viewing has been minimised. This is especially annoying if I'm on a call as the call instantly minimises and I have to drag the screen down to finish the call. Any ideas? Cheers!