Errors – 2012 Zombies vs Aliens Review

I am playing on my phone and i am on the second world and I am wondering why it won't let me upgrade I've read other reviews and it seems to be a problem on other iPhone 5 users and should be fixed, it makes the less fun because you have these low weak guys and can't upgrade but the enemy has high good troops other than that a great game
Review by Reynolds Family Rocks on 2012 Zombies vs Aliens.