Interesting problem with volume buttons--what's causing it?

My 'lower volume' button doesn't work properly. Pressing, nor holding the button down, will allow me to decrease volume. In order to increase volume, I have to hold the 'raise volume' button down, just pressing it won't change the volume.

To make things more complicated, this doesn't happen all the time. If I restore it or sometimes when I turn it on after charging it, both volume buttons will work normally, for a time. But the problem always comes back, usually within minutes of use.

My question is, what's causing this? I would assume that the problem is in the headphone jack/button assembly, but I simply don't know enough about electronics to be confident that this would fix the problem. Before I invest money in replacement parts I want to be sure that the problem isn't in the logic board or the software or something.

A while ago my iPod went through the washing machine. The battery has been caput since then, not sure if my volume button issues could also be a result of water damage.

Any suggestions/opinions/speculations about this are more than welcome. Thanks!