New DGX-660 with an odd issue.

So I bought a new Yamaha DGX-660 a few weeks ago, and one of the low D keys seems to be noticeably louder than all of the other keys. It's jarring. I grew up on an upright and a baby grand, and this is my first digital piano. Have you ever experienced/heard of anything like this happening? Can something like that be adjusted/tuned in the settings somewhere? I know it's kind of a strange question, but I haven't been able to find anything online to help yet. Thanks!!