Unity2018.3 Blenshapes will change model's normal,Unity

my 3D model changed normal in maya, and also contain blendshapes , then import the model into unity2018.3 , the issue occured. when I change blendshape , the model normal will alse changed . but I don not expect nomal changed. And also , this is not happend in Unity 5.6. In Unity 2018, the modle import param "BlendShape normal " is not usefull.,

get the same problem…our project stuck in this…