DDJ-RZX pitch drift

Hi, I recently bought a DDJ-RZX second hand and noticed the right hand deck 2 is suffering from some pitch drift.

• In manual mode (no sync) the pitch will drift up to .4 up/down when playing
• Switching over to deck 4 has the same problem but the drift isn’t as much (maybe .02 up/down)
• In Sync mode, if started on deck 2 will drift and show up on deck 1 as well.
• When you mix over to deck 1 it’s fine and when it goes back to deck 2 after that it’s also fine! But if you touch the tempo slider in any way it’ll start to drift again.
• I noticed in Rekordbox, when Deck 1 is playing in Sync mode (Master) there is a warning for ‘Invalid Operation, In Sync Mode Tempo Slider is only available for Master deck” so it looks like Deck 2 is still trying to drift.

My question is does this look like a software or hardware problem?  As I'm new to the RZX, I wondered if there was anything I could look at that I might have missed.  

I could leave it in Sync mode but I'd rather not.

Appreciate any help.

Rekordbox 6.0.2  (tried both Mac & Windows)
DDJ-RZX firmware 1.10
Driver 1.021 (Windows)