AD633 output offset voltage

Hi

 I am FAE in Japanese distributor.

Our customer produces his product using AD633.

He is calibrating AD633 at Vs+=15V, Vs-=-15V, X1=0V, X2=0V, Y1=2.5V, Y2=0V.

After the calibration, he test AD633 the condition is followings.

Vs+=15V, Vs-=-15V, X1=0.2Vsinusoid, X2=0V, Y1=2.5V+1Vsinusoid, Y2=0V.

X1 and Y1 sinusoid are 50Hz and same phase.

He found irregular AD633 device which showed W voltage shows under the calibration voltage.

Please see the wave picture.

Does the device violate the specifications?

If the device is normal, could you advice the cause of this phenomenon?

Best regards

N.Kokubo