@2x images not loading in some iPhone 4 devices

I've added both image.png and image@2x.png in my resource folder. My problem is, in some iPhone4 devices it is loading the image@2x.png correctly while in some it is t开发者_高级运维aking the image.png file. Please help me in this as I couldn't find any obvious reason for this.

Thanks in Advance

---

Run this test. Turn both devices off and restart them. They both should load the retina image if their iOS is the same version. I guessing the iPhone that doesn't load the retina image has a lot of background applications running. I believe if memory is below a certain threshold non-retina images are loaded instead.