DDJ SR - Left Platter Keeps Moving On Screen

Hi All,

I bought a brand new Pioneer DDJ SR about 6 months ago from Amazon and initially ( for a few weeks) everything seemed to work normally till it started causing problems. The Left Platter keeps moving on screen even when it has not been touched. I have tried using both Serato and Virtual DJ but the problem keeps recurring. I have Also tried increasing and decreasing the sensitivity to no avail. Quite recently ,it happened again at a gig and a friend just tapped the top of the left platter and the movement stopped for a while only to re-occur mid-gig.

What could be wrong ? Has anyone experienced this Issue. Would be so grateful for help. Thanx in Advance