Our VR project has a widget interaction component that acts as a pointer attached to one motion controller, and the trigger is used to press and/or release the pointer key on the widget interaction component. The other motion controller has a widget component that acts as a popup menu, and the menu contains a scrollable area using a scroll box.
As of 4.15.3, the scrollable area worked fine - the user could “grab” the scroll bar and move it up and down and the area would properly scroll, or the user could click in the above or below the scroll bar to make the scroll bar jump to that location, and the area would properly scroll.
In 4.16 and 4.16.1, the scroll bar is no longer draggable at all, and clicking above or below it to make it jump to that new location only works some of the time - typically if you try to drag it and then give up and click below it to make it jump, it doesn’t work, but if you click around to other UMG widgets for a bit and then come back to the scroll bar and click below it, then jumping works.
Even though the scroll bar isn’t draggable, it appears that some part of the interaction is working because it properly highlights and unhighlights as the pointer passes over and away from the scrollbar.
I’ve reproduced the problem in a simple (and clunky, sorry!) standalone project. If I open the attached project in 4.15.3, everything works as intended. If I open a copy in 4.16 or 4.16.1, the problem happens consistently.