Holding mouse button prevents onHover events

Normally on the hero selection screen, when the cursor hovers over an infobox for a hero or mercenary, the box enlarges and text appears which describes the unit.

If a mouse button is held down, and then the cursor is moved over a box, it will not enlarge, and text will not appear. The hover sound effect does occur, however.

Normally the gear icon for the settings window highlights when the cursor is hovered over it on the hero selection screen. The icon does not light up if a mouse button is held down prior to hovering over the icon.

The problem goes away when the mouse button is released.

This problem also happens in the game to the UI layer. If a mouse button is held down, and the cursor is currently hovering over the UI (army/production tabs, top bar, production selection box), certain UI hover events do not occur, such as the orange border which appears when the cursor hovers over a unit that can be produced. Map panning is also disabled during this time.

If a mouse button is held down but NOT while on a UI element, everything works.

And if the mouse button is released, everything goes back to normal (panning and hovering work).