Mistake at the end of the barn dance...

I just noticed this recently,which is a bit surprising,as I've seen this movie several times over the years. We all know the couplings in the movie are as follows-Adam/Milly,Benjamin/Dorcas,Caleb/Ruth,Daniel/Martha,Ephraim/Liza,Frank/Sarah,and Gideon/Alice. At the end of the sequence,when the girls end the dance by jumping into the arms of the brothers,all of the couples are paired correctly,except Ephraim/Liza-Frank/Sarah,when it ends the pairings are Ehpraim/Sarah and Frank/Liza...Not that we'll really ever know,but I wonder why it was filmed that way? A few theories-maybe the original script had the pairings of E&S and F&L,and it was changed during filming,maybe it was a mistake that wasn't noticed until editing,and they figured it wasn't enough of an error to bother re-filming,or maybe they thought that Tommy Rall(Frank) and Virginia Gibson(Liza) were two of their strongest dancers,so they paired them together for the number.Again,we'll never know for sure,but it's fun to discuss. :)