What happened to the gems?

Enjoy the game but since the last update, the gems are screwed up. I went through 45 waves, tapping over 100 gems, and at the end I only had 4 more than I started with! New wave, some gems get erased. I guess this is how you secure in-app purchases to continue the game. Not worth the effort!

Titiger01 about Goblin Defenders: Steel'n'Wood