I just saw your other post looking for a tute on trimming. Your star sections look perfect in that post so not quite sure where the wonky came into play for the center section. I would do as ckcowl states and (unfortunately) start ripping and re-sew in pairs. Do lots of pressing with lots of starch as all those bias edges can get out of control very easily.
I put a pin vertically through EACH intersection and then one flat on either side of the vertical pin before removing. Do that for each intersection as I come to it. And I agree with pressing seams open, especially on this one. Makes the center MUCH flatter to work with down the road.