Please open the menu, change to Settings > Input Device > Functions and reset the assignment in the Throttle line by clicking onto the O sign. You don't need a throttle input for the neXt because the rpm is defined in the flight conditions.

If you really need that, you can use the throttle input. Or you define two flight conditions where the head speed is defined and switch between these two flight conditions.

In reality, I always switch the head speeds by using flight conditions because then I can also assign the two different tail gyro values.