Z2 - Faders and cross fader playing up - From Ground Static?

Hi guys I scored apparently a 'as new' Z2 off the net but after using it a few times its all of a sudden got weird fader issues - not smooth volume transitions, cross fader sometimes doesn't work at all - channels bleeding - the works it was bad. This was on pass through and through traktor.
I turned it off for a few hour set it up again... and everything seems to work ok now!
Is this problem going to return? Has anyone else seen this intermittent behavior before?

there is one thing I thought for the reason - I didn't have my phonos hooked up with ground - do you think the static from the turn tables could be causing the mixer to freak out? I mean the mixer does look pretty new (mind you there is some corrosion on the input terminals at the back which means it was left out of the box for sometime.)