Moving a thumbnail in Grid

Here's an annoying problem I'm having with PR2019 regarding re-arranging the order of images in Browse Grid display.

I select Custom sort at the bottom of the Grid view. I grab (L-Click + Hold) a grid image and move it. I see the yellow bar at my intended place and I drop the image onto it. Sometimes the image moves as intended; sometimes it moves to an unintended location; most of the time it does not move at all.

I've had this problem since this feature was introduced in PR2018 (?). Problem reports to On1 Support result in "We're looking into it" and are of no help.

Anyone else having this problem? Any suggested fix?