My PS brush freezes for no reason ALL the time. I must switch between a different screen almost to 'refresh' it. What's going on?

When working in PS, my tools (brush/eraser) stop working and the only way that I can continue to use them is to click into a web browser or Indesign, click on something, and go back to PS. I had been working on an iMac and just bought a new Macbook Pro, and even with the software reinstalled from CC, the error still persists.

Believe me, nothing is selected at the time, and no masks are being used. I'm an illustrator and primarily use the brush and eraser tools. It's a constant frustration when I have to exit out of what I'm doing to 'refresh' my brush.

Does anybody have an idea of what could be going on?

Thanks in advance!