There are two versions of Rambam at the end of Hilchot Melachim (12:5). One says
?????? ????, ?? ???? ?? ?? ??? ??? ????? ??? ???? ??????–?????? ???? ?????? ????, ??? ??????? ?????? ????. ??? ???? ??? ?? ?????, ??? ???? ?? ?’ ????. ?????? ???? ????? ??????, ??????? ????? ??????? ???????; ?????? ??? ????? ??? ??? ????, ????? “?? ???? ????, ??? ?? ?’, ????, ??? ?????” (?????? ??,?).
Another says ???? ????? ????? ??????.
So it seems that there will not be sin as such. It could be that some will not fulfill mitzvot in the absolute best possible way.