The gyro sensors do not seem to work correctly.
The rudder servo does not react or reacts very slowly to rotation of the helicopter. (The same happens to the elevator axis.)
Probably the gain of tail gyro is too low.
- Check assignment of gain channel and adjust the gain in the transmitter as described here.
- Check for correct wiring or setup of tail gain cable/channel.
Additionally when the elevator doesn't seem to work either, maybe the wrong mounting orientation has been selected. So select the correct mounting orientation in Setup menu point A.