iPod Nano 5th gen. - sound problem

My iPod Nano 5th Gen. has the following problem: sometimes the sound gets weird (when the headphones are on, when they're not, the sound is too low). The sound seems cracked and muffled. The only way to make it work again is to squeeze the area in the bottom of the screen, even thought sometimes it's difficult to make it work again.

This started happening after I put the iPod in a shield case (made by Belkin, which I believed to be a brand of trust when it came to device accessories). The case was too tight for the iPod because it was difficult for it to close. Even so, after I was able to close it, the sound on the iPod wasn't working normally like it should so I took the case off. The sound still wasn't ok so I found that way of squeezing it in order for it to work again. I returned the case to the store.

But the problem seems go on again, specially after I turn it off (when i press the play bottom on the click wheel for a couple seconds) and if I use the click wheel with the iPod resting on a plain surface. I believe this must be a connection problem between the device and the sound.

I would like to know if any of you ever had this problem, what else can I do and, if there's nothing I can do to solve it, if you think that it's worth repairing the iPod in an Apple support center (because, with the experience I've had with another device that had a problem, sometimes the price of repair is so high that it's cheaper to get a new device instead of getting the actual one fixed).