you have kept the overlay anchor poit in original position 00 which is the lower left corner therefore it does this seemigly shift while scaling
so you can eather change the anchor point to be in the middle of the overlay or you will have to shift it together with the scale to the right position
changing the anchor point would mess up your current spots of the overlay and you would have to redo it more.
So in your case I would probably go to simply move and scale it in the same time
fine the finals spot where you want the overlay to be after it scales to the max
and move it to that position in the same time as you scale it using & so it will happen together
&overlay ONE SIZE FITS ALL shifts to # # in zone 1 in 0.4
&overlay ONE SIZE FITS ALL opacity 0.33 in 0.4
@overlay ONE SIZE FITS ALL scales to 6.274 6.274 in 0.4