Visual styles disabled, have detail view, have some files in the folder. Click on first file by mouse, then by holding shift select for example tenth to have them selected all. Then try to hold shift and key up to move up (unselect some files). The tenth clicked by mouse stay still selected. The same in opposite way. It does not happen in list view.
Confirmed, and does seem like the wrong behavior. I've added to the list to look at. (Needs some time spent on it as the logic behind shift-selection is quite fiddly and needs focus and testing if we change it, to avoid breaking it in some other way.)