Mouse and touch support seems to become unresponsive when the editor is running on a 4K panel. Certain play modes will allow click events to work while others do not when running on a 3840x2160 display.
Repro with attached project:
The success line prints, mouse location is modified
Success line prints, mouse location is not modified
Workflow Repro (not using attached project):
In 4K different play modes seem to offer different results. For example just using PIE seems to work ok but using play in new window seems to be broken.
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-56329 in the post.