There appears to be a problem with the hex resize tool where the fine control for resize a hex left or right (Ctrl + Arrow) also appears to completely move the hex left or right as though you have also held down the Shift key. The Resize Up or Down appears to work fine.
I tried this in 3.6.19 and 3.7.1 and resize left/right features dont work in either.
I think you will find that the resize is anchored at the origin of the hex grid, right off to the side of the map, so that unless you are looking at the very top left corner of your map while you are doing this, the hex grid will indeed ‘appear’ to move left or right.The further right you are looking, the ‘faster’ they will appear to move.