This glitch also occurs on the login page (not the lock screen) except my first monitor (The one on the left) is completely unintelligible. I shall get a screenshot of the login screen (If possible). The odd thing I found about these glitches is they didn't occur when I was using Linux Mint, but started occurring when I was using Ubuntu. If anyone can explain what is going on and how I can fix it, please do. Specs and Other:Gist
This looks a great deal like a Graphics Driver glitch.
The current Zorin OS Kernel may be too new for your Radeon Card.
You might try installing the 5.8 kernel: