Noise on my image. PS? Wacom tablet? High Sierra issue?

[LesToil]

Greetings. Since getting a new iMac and downloading Photoshop CS6 from Adobe I keep getting these little "noise" squares/garbage on my PS window that are constantly there. If I enlarge my image or move my image around the noise with disappear and appear elsewhere in the image.

Is this a PS issue? Intuos pen/tablet issue? High Sierra issue?

Thanks very much in advance.