Please explain why the shadows of body parts move when the model's eyes blink

I’m an amateur and I use Unity to create videos.

When I load the model into Unity and use a blend shape to make the model’s eyes blink, the shadows on the rest of the body move.

Can this be resolved with settings on the Unity side?

A similar phenomenon occurs with multiple models.

Similar phenomena occur with multiple models.

If you have any advice or tips, please share them.

Maybe consider adding a screenshot (or video, try Screen2Gif) to beter illustrate what issues you are facing.