[Spoiler]The man in the end of the game

[Thaliur]

why did the flashlight decide to malfunction? Mine had full batteries and everything! (of course, the easy answer is so you can't see the guy, but still what would have caused it to break?)

Over heating, for example?

It's really hard to get a flashlight to overheat, at least those I know so far. And Philip as a modern scientist would probably use one of those LED flashlights for efficiency and reliability (and geeky style ^^), these barely warm up. Oh, and it's Greenland, I don't think these caves have central heating that still functions.
Maybe it got a slight power surge when cutting the wires that keep the door shut, weakening the electric components, and causing them to break down at a convenient time.