Replacement trackpad is laggy

Hi! I purchased my Mac from a fellow friend who needed money. And he gave it to me with a broken trackpad on the top left edge. Coming back to today, I purchased the replacement trackpad and I could and did replace the factory one. Thing is that when installed I proceed to test it, and it's somewhat like laggy from the half to the top of the trackpad itself. (Don't know if I explained myself properly). Plus I couldn't do a drag and drop action using two fingers. What could it be? Installed back the factory one and it works like a charm. Is it the trackpad thats not fully original or is it defective?

Thanks.