If you have tried to align the overlay with the main spectrum by changing the “h. offset”, you are in good company, but you are completely wrong.
The purpose of the offset is to create stacked plots; for example, to show the main spectrum in the left half of the page and the other spectrum in the right half. For this reason, the amount of the offset is measured in screen points, which have no fixed relation with the experimental points.
Nothing prevents you from misusing the offset. You could use it to momentarily align the peaks of two different experiments. This is conceptually wrong and a sure cause of troubles. As soon as you change the zoom factor, you lose the alignment.
If you need to align two experiments, change the frequency scale of one of them.