Sprites inconsistently turning black on iOS

On the project I’m currently working on, a number of sprites are rendering as black rectangles, irrespective of their original image. Every time the project is run on iOS, at least one of the sprites comes up as a black rectangle, but which it is is inconsistent.

All of these sprites have been created by assigning a sprite to an image object on a canvas, so this doesn’t look to be a code issue, but who knows. Additionally, it may be related that there is a sound effect that (again, inconsistently) fails to play at the same time.

Any ideas as to what could cause this?

I’ve experienced black textures on Android. It seemed to happen when memory was getting very low, if I used more memory, the game would crash. If I reduced memory, then the black textures would go away. So from what I’ve seen, black textures mean the application barely has enough memory to run and on the verge of crashing.

Although, it maybe other causes, perhaps lighting, or a shader problem.