Wavery Sound on Playback

I love this recorder, but mine almost immediately displayed a defect. The sound wavers, like a tape recorder whose capstans are dirty or oily. I can't imagine why a fully digital device would exhibit analog behavior, but it does. The problem doesn't seem to stem from the recorder's position or movement as the recording is made.

Wavery recordings can still be deciphered, but they're a pain. I'm seeking a replacement unit.