Original: This problem has largely been eradicated with the advent of the "new series" version, as its remotely controlled dome and eyestalk allow the operator to concentrate on the smooth movement of the Dalek and its arms.
Simplified: The latest model of the costume still has a human operator within, but the movement of the dome and eyestalk are now remotely controlled so that the operator can concentrate on the smooth movement of the Dalek and its arms.