I am experiencing the same problem. I have tried a number of driver versions, including the one installed by Windows Update. If I move the 6900 XT card to another system the problem does not follow it to the other system. If I install an NVIDIA GPU in the system that has this issue the problem goes away. The affected system is a triple-monitor setup. Enabling or disabling Eyefinity has no effect on the problem. Disconnecting two monitors and using only one does not affect the problem.
So, in my case it is directly related to the AMD video card and something about the system that just doesn't like it. I tried suggestions found when searching for a fix, such as disabling Office graphics acceleration and enabling Clear Type, and neither of those things work. This is a multi-boot setup (and so is the other computer). It happens with Windows 11 and Office Pro Plus 2021 and it happens running Windows 10 with Office 365. The only solution I have found is to use an NVIDIA GPU in the system that suffers from this weird glitch.
It is a text rendering problem. It is not related to overtyping or toggling insert, as it only temporarily corrupts the view of existing text that has already entered and is present to the left of where new content is being added. Scrolling through an email or Word document, or navigating an Excel worksheet, is not a problem. The issue only surfaces while editing and typing in characters is when the display of text on screen becomes temporarily corrupted. If I am typing in Word, for example, characters to the left that I have already entered will disappear and shift or leave white space where they were entered, but a few keystrokes more and that text reappears. Sometimes there will be artifacts and text from another area will momentarily overlay the text that I entered 1 or 2 seconds before.