I have the same issue, vertical sync is activated by default, must be something else. I have tried several other alternatives, aka Scaled & more memory, all failed.
Then I found this post indicating a solution like so "set 3d acceleration from directx10 to directx9, when I did this the text corruption was completely eliminated.". I can confirm that this solution did work for me as well. Source : https://forum.parallels.com/threads...e-scrolling-after-upgrading-to-sierra.338230/
Last edited: Oct 16, 2016