You can try this, at 1st my S-Pen accuracy no problem, after few days when I use I see the offset problem as what you guy seeing. Try below:

Go Setting > Pen Settings > Dominant hand > If Right chage to Left, if Left change to Right > press return button until home page > Press & hold the button on you S-Pen then touchs(hold your s-pen 90) the Home page screen to print screen > tried to draw something on the printed screen(NO need to hold your s-pen 90) > no need to save just go back to Home Page > Go Setting > Pen Settings > Dominant hand > If Right chage to Left, if Left change to Right > press return button until home page > Press & hold the button on you S-Pen then touchs(hold your s-pen 90) the Home page screen to print screen > tried to draw something on the printed screen (NO need to hold your s-pen 90),  this has solve my problem, no more offset problem till now.

No harm to try. Hope this will help. Don't know the theory behind, don't ask me. 

Just let us know if this work or not work for you.