Currently even the shortest drag on an image in the grid view will trigger the "reordering" operation (where the blue line appears to indicate where you want to place the image. Not only is this function too easy to call accidentally (especially when using a trackpad where accidental touches can register as a click/drag), but once it is called, it's unintuitive to cancel without consequences (you need to drag the image to an area where it doesn't allow you to drag an image to, such as the top bar). If you try to drag the image back to where it was (which feels more intuitive), you're punished by the sort order switching to Custom Order, and you then have to go back and set the sort order back to what you had.
tl;dr: the sort order should only change from a click/drag operation if the image is actually dragged to a new position, and not when it's dragged back to its original position.
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