Dynamic shadow offset from casting surface

First of all, thanks to everyone!:)I’m not good at English.
*Engine version:4.26.0 Divece:**Mobile phone(*Google pixel2 ) The image below is a mobile phone’s screen taken by a camara.
Level settings: Stationary Directional light
The shadow from Dynamic object casting incorrectly,it doesn’t start from man’s feet as you see. And the distance (A-B) will change when camera turn around the man. There’s a another issue not showing in the image.There’s a another shadow will be appear on the man’s body while one shadow is casting on the ground.It will appears when camera turn into a specific position.
This issue show up after my project move to UE426 from UE425.
Thanks to all of you guys!