Realigning a stacked piece to a grid

This seems like a bug to me but maybe I misunderstand how grids, stacking and snapping works.

I have a couple of pieces stacked on each other on a map with a hex grip.

I changed the hex grid, so I want to re-align the pieces. If I move them manually they behave as I expect… snap to the new X/Y location and remain stacked with each other.

If I move them through automation (a GKC linked to a small move via Send to Location), the pieces get re-centred in their hex but become unstacked. A repeat of the Send to Location, just on the overlying piece, causes the two to re-stack.

Is this expected behaviour, I wonder ?