Game logic not updating on mobile devices

Hello, I'm getting a strange bug when I run my game on any mobile platforms (andriod, iPhone, iPad). For some reason, when I run my game on a mobile device, if your not touching the screen, it's not updating the game logic. If I run my game on the web, or as a PC standalone, everything runs fine however.

For example, I have some monsters randomly spawning around the screen, walking towards the middle of the screen, and when they hit the middle of the screen, they explode. If the user isn't constantly touching the screen, the monsters don't spawn (only if they are touching the screen, do they spawn). Also, if the user doesn't touch the screen for awhile, then touches the screen, all the sudden, all the monsters that were supposed to spawn during that period in which the user doesn't touch the screen, all spawn at once, as if all the updates for monster spawning were queued up until the user touched the screen.

I have no idea why this is happening. Has anyone else had similar issues, or have an idea as to how to fix this problem?