How do you get a water leak in a spacesuit helmet?

The LCVG is wholly enclosed by the outer suit. The fact that our almost-first-man-to-drown-in-space described the feeling of abnormal moisture as starting at his head, rather than some random tube somewhere on the body, suggests that the PLLS, which is responsible for removing water vapor and carbon dioxide and returns processed gas at the back of the helmet was the source of the problem, maybe a leak in the heat exchanger portion that handles cooling the LCVG circulating water, maybe the condenser/slurper arrangement not performing, rather than a peripheral leak in the LCVG.

(Disclaimer: I am not a rocket surgeon)