Photoshop Bug - Clicking textbox reduces resolution?

Hey, I was wondering if anyone could help or were having a similar issue.

I was working on a .psd file this afternoon when randomly came across a bug that is stopping me from being able to work. When I click a text box to edit the content, there is a quick split second black flash within the photoshop window, and the resolution of all the content drops horribly. Photoshop then also becomes laggy and slow to navigate.

This issue is not due to the file, as I've tried it with other files. It's also not restricted to my work machine, (a macbook pro), but also my personal machine (also a macbook pro).

This has never been an issue until this afternoon. I have Creative Cloud set to automatically update. I tried updating my work machine to be on the latest OSX, but this hasn't helped either.

I've attached images of the before and after,

Thanks for your help