Try this - play the timecode through your mixer in the phono input so you hear the tone, and let it play. Do you hear any wobble or change in the tone? Speeding it up / slowing it down should change the pitch, that minor variation is what you're looking for in just regular playback - this is to troubleshoot if the turntable itself is the issue or if you should chase the problem down the chain.
Next, check the calibration scopes in the rekordbox DVS preferences to see if they're round and clean. Maybe post a screen shot of those?