Touches on windows generate 2 mouse events.

The problem is that windows supplies both a touch event and a mouse event for each touch. The engine then handles touches as mouse input so that UI elements can work correctly on touch platforms.

1. Click a button using touch on a touch monitor.

Result: Button is clicked twice.
Expected Result: Button is clicked once.

Touch input fires click event twice on Windows 10

OnClicked/OnPressed of UMG Widgets fire twice on Windows 10 with certain touch devices.

Touch input fires click event twice on Windows 10