@Nipuni ,
This isn't normal behavior, have you changed or added gallery in Scroll card or any other place that shifts in Y co-ordinates?
Do you have same problem when you are in App editor?
If yes, pls do check you X and Y co-ordinates carefully for each control (properties on right pane) if used Parent property then check the instance of X, Y, Height and Width property at that instance.
Although its tricky to know where things went wrong, do you face same issue when you add a Sample gallery on the same page and see the offset change?
If yes, then your parent if making changes on the Gallery control.
Hope this makes sense