Developers seem to have added a new feature which throws you out of the game whilst watching an advert. By my estimations this happens as such: 65% of the time you will get your reward. 25% chance of being kicked from the game after the advert plays (no reward). 10% chance your phone will freeze just after clicking on the advert. Contacting the developers will not help. If it's any consolation, it isn't just your phone/game. There's an equal chance of it happening to any player.