The Tiger II can be a very aerobatic plane. I believe you answered your own question when you mention the play in the torque rods. Torque rods are a terrible way to actuate a control surface and have natural play built in. The rods themselves twist, inviting flutter. If possible, I'd retro-fit individual servos in each wing panel, with direct. straight line rods to the ailerons. Use the shortest servo arm and longest aileron control horn you can and still achieve the movement you desire. If the problem continues. you can try counterbalances at the ends of the ailerons. Sometimes cutting the end of the aileron back at a 45 degree angle helps, too. Eliminating flutter is not an exact science, rather a "cut and try" exercise.

Good luck with it.