A simple page: body/container (set to flexV)/single column - 2 row grid/two images.
In designer I step down through the sizes to phone V then step back up to phone H and the images stay phone V size. Then step up to pad size and the images are still phone V size as they are when I step up to computer screen size.
It’s not a grid issue nor is it the first time it’s happened.
It’s happened many times with a very similar page using flex opposed to grid.
In all cases the images resolve to their correct on screen size by refreshing the browser page.
THAT STEP - WORK AROUND - SHOULD NOT BE NECESSARY
But such are the problems of working with web based software