Creaking sound coming from dashboard area

I have a creaking noise coming from the right front dashboard area. This occurs with any forward motion changes in speed such as starting from a stop, coming to a stop, or acceleration/deceleration in traffic. The dealership has worked on it 3 times, but is unable to solve the problem. they have investigated various possible causes including the glove box, front passenger window, ventilation conduit on that side, etc. They say there are no service bulletins for this problem. Has anyone out there experienced this or have ideas on how to address this? Oddly enough, during wet weather, the problem goes away, leading me to believe that friction between parts is the source and it is somewhere that water can get to and lubricate the contact points. I have explained this to the service tech, but they cannot seem to locate the source. Thanks.