This has been an issue for a while. I'm using Outlook as part of Office 365 on my desktop, Dell XPS 8950. While writing an email, all of sudden, text disappears or gets distorted (e.g., some part of the text is shown and the other part is not). After scrolling up and down the mouse wheel, it usually returns to normal.
I've searched for a solution and found almost all suggested solutions say that I need to disable "overtype mode" as below. However, both options were already unchecked but the issue does not go away.
Text disappears as I type (microsoft.com)
TYPED TEXT DISAPPEARING BEFORE MY EYES ALL THE TIME WHILE TYPING EMAIL - Microsoft Community
If you know other causes or solutions, please let me know. This is really annoying and refuses to go away. If standalone Outlook (e.g., Office 2021) does not have this issue, please let me know. Thanks.