Greg Low has a workaround for an annoying problem:
Once again, I’m seeing lots of customers reporting screen repainting issues in SQL Server Management Studio (SSMS). It mostly seems to affect version 18 but I’ve also seen it in version 17. And it’s most prevalent on Windows 10.
The typical issue is that you click on another open tab, and the contents of the tab doesn’t repaint. You are still seeing the previous tab. If you click into the tab, you start to see bits from both tabs.
Click through to see the fix. I’ve seen this issue pop up though I don’t remember seeing it on the latest version of SSMS 18…though now that I say that, I’m guaranteed to have the problem hit me today.