![Image](https://forums.factorio.com/images/ext/56a203cdc538e760428bfea6453d4e68.png)
How to reproduce
1. Set tooltip delay to maximum (500ms) and open a game where there are items in the hotbar.
2. Move the mouse cursor from outside the hotbar area onto an item and let it dwell for a bit and let the tooltip pop up.
3. Move the mouse cursor over another item and look to see if it's highlighted. If the new item is highlighted go back to step 2 (it may take a few tries). Notice that clicking on the unhighlighted item won't pick it up and the tooltip is still for the old item.