It's irritating when this happens. We expect "new" to be perfect and free of problems. I bought a DL-103 from AudioCubes years ago and it happened to me, but I don't remember hearing a difference between channels.
Should you complain to the vendor? I don't have a strong opinion one way or the other, but I wish you luck.
Should you complain to the vendor? I don't have a strong opinion one way or the other, but I wish you luck.