There are several potential causes for this behavior. A very small amount of vibration will normally be felt in the right handle, because it is directly connected to the motor. This should never be seen in the actual picture, though.
When the vibration reaches a certain level, the Helix may not be able to respond to commands (RC, joystick, motion of tilt handle, etc.). At this point, there is so much motion due to vibration that it cannot respond appropriately. Reducing the vibration may make your Helix respond to commands properly.
Potential symptoms and causes:
The Helix acts normally when facing directly forward, but has vibration or acts erratically when tilted more than ~30 degrees up or down – This is almost always a problem in balancing of the Helix. Usually the Helix is bottom heavy, and in the normal position facing forward, the motors are strong enough to compensate, but as the angle increases, it requires more forces to overcome the imbalance. To fix this, rebalance the Helix on the tilt axis as per the instructions in this article. (Note that this may also happen in other axes, but is seen much less commonly.)
The Helix has vibration when facing either directly down or directly upwards (or close to these positions) – If you need the ability to point the camera straight up or straight down, see this article.
The Helix acts erratically in the tilt axis and the motorized handle is in the user’s left hand – Turn the Helix around. It designed to only be used with the motorized handle in the user’s right hand.
The Helix has a slight vibration in one or more axes, but is still responsive to commands (may not be responsive in extreme cases) – This is most often caused by improper PID values on the Basic tab of the GUI. Start by determining the axis with problems. If it is not visually obvious, then gently touch each motor one at a time to determine which is vibrating. Consult the PID tuning article for instructions in determining the proper PID values.