Hi,
I am also experiencing an issue with this async draw flag activated (tested on mojave and bigsur) that appears to be the same announced in this post Incorrect image colour rendering in Pro Tools. All UI colours become slightly lighter with the flag activated. I was only able to reproduce it in ProTools Ultimate (2020.9.1 for instance) on several machines. I also noticed that the first paint, when the plugin is instantiated, is correctly coloured (no lighter colours) and only the following paintings introduce the colour problems.
I do not have any custom colour profiles for ProTools and this happens in both light and dark mode of PT.
Any clues on what this might be?