Red Areas on-screen in Catalina.

I have a persistent rendering problem on my MacBook Pro, running Catalina (fully updated). I'm seeing red boxes/fields of red in Email and Safari. They totally cover up content, and can be partly eliminated by selecting or using Cmnd-A which forces a re-rendering of the content. This bug started with Catalina, but I don't recall if it started exactly after upgrading, or if something else triggered it. Has anyone else seen this issue? Any idea how to get rid of it? It's been more than a month and no updates have had any effect. I also can't find any mention of it elsewhere, so I haven't had any luck in diagnosing it.