CDJ-2000 Nexus Drifting Problem

Hi all,

I've recently gotten my hands on a pair of second hand CDJ-2000 Nexuses. Unfortunately, im experiencing a lot of drifting of tracks even when they are set at the same BPM and im not sure what to do, as even over 4 bars there's enough drift to need adjustment. It's ruining my mixes.

For starters, i've done the following:

• Both CDJs running latest 2000-Nexus firmware v1.43
• All tracks analysed using latest rekordbox 5.8.3 in "normal" mode, not dynamic
• Master Tempo on and off, the same issue
• Same BPM (to the same decimal point), "approached" the BPM from the same direction on the slider
• If one track is behind when they are set to the same BPM, even if i speed it up by 0.1 increment, that track is then too fast and needs adjusting backwards
• Tempo slider range set to +/- 6%

I'm at a wits end here. Any help would be much appreciated as they are just unusable with with such drift. Could the CDJs be faulty?