To be on the safe side,this to me looks like there is a sag in the ceiling. Is this a bearing wall that someone did not make the beam large enough? I do not know, but if I where you I would look into it.
As for the trim if it's good to go, just install the crown , You will never notice it when it is finished, actually happens alot in older homes, just split the difference best you can and call it done.