[Dangerzone]

did you zoom in on the stain (with the normal cursor)or are you still in the view with the victim


and you have to click on the stain with the uv light equipped

and click around thae stain as well, it is like the fiber
sometimes it does not work when you click on the dead center of the stain

and make sure you are using the uv light and not the regular flashlight


i can tell you that it is an error that you are making,
because game glitches ure usually acompanied by lockups and/or graphic glitches