See attached example. On start the scrollbars will typically shadow the content of the itemview. In some situations it may stop doing that when we apply the style sheet again (second button) or the dialog is resized (not always depending on external screen and co-coincidence - at least in Qt 5.9.4 - I could not reproduce with recent 5.12 build).
Also notice that the horizontal scrollbar is not shown at once though it should be.
Another issue related to this is that if the program hides the horizontal scrollbar, then the horizontal scrollbar range is still changed when/if Qt realizes that the vertical scrollbar needs space - which still leaves an area to the right hidden behind the scrollbar. (though the content should never have had this width). This can likely be reproduced by setting column count to be 50 + move horizontal scrollbar to the right ... and apply the stylesheet again. Notice that the horizontal scrollbar no longer has the maximum position. (+imagine that this scrollbar was hidden ...)