i am not sure, since i don t have neither the keyboard or the manual with me right now, but i think you might need to edit (re-record) the measures you want only by entering song mode, not back seq. mode.
that means you need to redo every anoying track by yourself, not by the arranger. i think punch in rec is available only this way.
but like fran says, is much more easier to correct everything that's wrong using a computer software.
good luck!