The valves in this stove are a big source of frustration, BUT there seems to be an easy fix, and once done the stove is perfect....just what you expect from Coleman.  All you have to do is use a Phillips head screwdriver to remove the knobs on the valves.  Then unscrew the brass nut that secures it to the front of the stove.  Now back out the valve stem using the knob and remove the stem that has two O rings and the brass needle valve.  Take a clean paper towel and wipe the gunk or the valve lube off of the O rings thoroughly.  I blame the lube for the problem.  The rings were in good condition.  I then applied a tiny amount of silicone based plumber's grease, but you have to be sure you don't use one that is petroleum jelly or it can ruin the rubber.  I bought a tube for a few bucks on Amason.  Then I twisted some of the paper towel into a point and swabbed out the inside of the valve, but don't leave any paper in there or you are in trouble.  Don't use a Q tip either or the fuzz may come off in there.  Here is link for the silicone lube: