Thanks for playing the game, and keeping with it even if it's hard to play and with a frustrating gem physics. and Thanks a Lot for the feedback.
I still think that the problem is not from thrown the gem but from the "physics of the gem". I knew that was a bad physics from the first day but I had to keep up. I used the RigidBody but, and there physics made the gem movement unpredictable. I was planning to replace it with KinematicBody and create my own bouncy physics, but the time wasn't in my favor.
The idea the brothers suck the gem if it close to theme seems a good idea. And also the game needs some check points (I runout of time before I make them).
I will work on fixing the game and adding more mechanics with more levels in the future.