It kinda does sound like the stabilizer is making some noise, but I still think the reason it sounds different is due to it's placement.
I did notice that the backspace stabilizer seems to be a bit 'looser' than some of the others, meaning when the cap is off it flops back and forth a little more freely. Some of the stabs I can position upright and they will hold there, while the backspace key will lay back down. Not sure why this is since there doesn't appear to be any damage to the stabilizer.
Oh well, this is a used board and the overall effect is really slight, but noticeable (especially if you type like I do!)