Tempo fader deck a delay in response and random tempo skip

Hi,

Since a while my Traktor Kontrol S2 is giving me a headache. The tempo fader of deck A (hardware) is responding with huge delay and with very small steps of tempo change. I push the tempo up or down and on my traktor software it is increasing/decreasing very slowly and with very small steps (it seems exponentially, the bigger the increase/decrease, the faster the tempo changes, however still very slow). I could kind of live with that, but what is even worse that since a few days it randomly changes my tempo to where the tempo fader (hardware) at that moment is. Very frustrating when I have my tracks in sync and suddenly a huge tempo drop/increase.

I have uninstalled everything (I have the latest update from native instruments). Reinstalled, once with my previous settings and once with all settings deleted to see if it is a software problem, but still no solution. I tested it without the latest update and with the latest update and the problem still persists.

Can I rule out that it is any software problem by now? Or could it still be a software problem? Do I have any chance of fixing this myself? I am not sure about the Warranty cause I bought it almost 2 years ago. Any help would be highly appreciated.