valve problem wtf? im stumped.

on my friends truck his front valves are mounted like this. the problem is the front left side is leaking air out of the outport causing it to drop over time. all the fittings are connected properly and its not a problem with the valve since he just bought a new valve and has the same problem. they are smc 10mm 1/2" valves. ive also tried switching the valve around but didnt help. anyone know what can be wrong, it seems like ive tried everything.