Disappearing text in Office for Mac

I have recently upgraded from Mac OS Catalina to Big Sur on an iMac late 2014. There is no rhyme nor reason for the text disappearing from opened Word documents. The words will reappear if I scroll up or down the page and return to the original location and then pff! they will disappear again (see attached screenshots). I'm a language editor and this activity is making my life very difficult.

Is this an issue of incompatibility between Office 365 and Big Sur? 

Can it be resolved easily?

Or should I simply delete the app and re-download and keep my fingers crossed it won't happen again?