Bpm moving around when using CDs on the CDJ900 Nexus

Hi,

Can anyone tell me how to solve this issue that I had, my friend has CDJ900 decks (Not nexus), when i use my CD's on his decks my mixing is flawless. I recently had a gig in Thailand (I'm in the UK so flew out there for it) and they had CDJ900, but the nexus version and it was an absolute bloody nightmare, the bpm was moving around massively on both decks using CD's, it was impossible to get the beats tightly matched as i was constantly adjusting the decks bpm up then down.

For example lets say the bpm was 138, it would be moving constantly from 139.9 - 138.4 on both decks. It was a disaster. A guy there said, "oh here they generally use a computer and there's no problems", I do not use computers, I'm oldskool. Bring back vinyl (lol).

If this happens again how can I sort this issue?

Thanks in advance