Fanuc says:
(Note) Make correct connections between a servo amplifier and motor used. If a wrong combination of an amplifier and motor is used, a malfunction such as motor vibration can occur, thus causing a failure.
They also say:
In this manual we have tried as much as possible to describe all the various matters. However, we cannot describe all the matters which must not be done, or which cannot be done, because there are so many possibilities. Therefore, matters, which are not especially described as possible in this manual, should be regarded as “impossible”
(Even if you are doing it)