When running Parallels 12.2.0 with macOS Sierra as the guest OS, I see windows that are blank, partially blank, or scaled improperly (zoomed in, magnified) in some apps such as non-Safari web browsers (Firefox, Opera, etc.). The behavior is consistent, either working properly all the time or improperly all the time.
I am guessing that apps handling their own window-drawing rather calling upon Apple's usual drawing libraries is the cause of the bug.
Is there any trick to getting the contents of these apps’ windows to appear correctly?
Brave 0.18.14 browser
In contrast, some apps including some web browsers draw properly.