Photoshop CS6: Random displaced glitchy blocks keep appearing on canvas (macOS)

It's most problematic on big, big images, like my current project, which is 5000px wide. Random things makes the canvas seem to error out a little bit, but mostly it comes up when I do things with layers--add, delete, make invisible, make visible, rearrange, change opacity, etc. They randomly generate any time I do one of those things. If I draw on an area  with blocks, they vanish, but only around where the brushstroke was made. Sometimes they disappear or reappear depending on the zoom. This is a real problem because it keeps obfuscating the view of where I want to draw.

I've tried googling to no avail. I feel like I'm the only one with this problem.

It's Photoshop CS6 and I'm drawing on a new Macbook Pro with a Wacom Bamboo.