My daughter bought a nice used GE fridge (GSHF6HGDCCBB) and it works just fine, but when a cooling cycle starts there's an odd "PEW! PEW! PEW!" noise that happens from under the fridge, like a pop-off valve opening or something? Sometimes only once, sometimes 4-5 in a row, sometimes none. The fridge works perfectly, but the sound is driving us nuts. It's definitely a mechanical sound, not any "alarm" from the electronics. Any help is greatly appreciated!