Colorsoft (16GB) slow and unresponsive at times

I was using a PW 12 signature edition and just purchased a Colorsoft 16GB. Pages turn just fine, but the pinch gesture to change font size doesn't work half of the time and the screen often becomes unresponsive or extremely slow. I have restarted it several times and it will be more responsive for a little while until all of the same issues come back. Even this last time that I tried to restart it, the screen wouldn't respond when I touched "restart", so I had to hold down the power button for a long time. Is this a known issue with the Colorsoft? Or did I get a dud?