Word randomly duplicates lines of text, Excel won't allow me to type in cells and cells appear empty even when not (Office for Mac)

Hello,

I'm working in Word and Excel for Mac Version 16.51 - part of MS Office 2019, not 365. I'm on a 2020 MacBook Pro with Big Sur 11.4 (but these problems have been occurring since I was using Catalina).

I'm having numerous recurring problems with both Word and Excel. I haven't seen any pattern in terms of when or in what type of file these issues occur. Note that I edit other peoples Word docs with Track Changes on all the time. For Excel files, it's rare for me to work on anyone else's files - I always create my own, whether from a template I've created or from a blank spreadsheet.

In Word:

• Sometimes the cursor disappears and will only reappear if I close the document and reopen it.
• Sometimes when I try to highlight text (whether a word, line, or paragraph), Word doesn’t highlight it. It may be able to highlight above or below the text I want to highlight, but it’s as though what I want to highlight just isn’t there, though I can see it. I can edit the text, but I can’t place the cursor to know where I’m editing; it’s only after I’ve made the edit that I can tell where it was done.
• Sometimes it’ll give me a duplicate of a row, right above the existing row. I can’t highlight the duplicate to remove it; I can only work on the original row, and as I'm working on the original row, the same changes are occurring in the duplicated row. To get rid of the duplicate row, I've got to close out of the doc and go back in.
• Sometimes in the middle of typing, Word jumps down to the end of the document without my having hit any key that would cause that to happen.

In Excel:

• When I get to the bottom of the rows that are visible on the screen, instead of scrolling to show the next line with every line that I add, it will scroll to the next available line, then partway through inputting into the first cell, it will skip to another open spreadsheet and begin inputting in that spreadsheet. It has happened often enough that I know it's not some random keystroke on my part.
• Sometimes I can’t click on a cell. I can click on a nearby cell, then use the arrow or tab keys to get to the one I want, but I can’t just click on it. And sometimes when I click on a cell, the cursor shows me in the cell I clicked on, but the data I’m entering in the cell shows in the cell below the one I’m entering it into. When I hit return or tab to move to the next cell, the data shows up in the cell I clicked on - just not while I’m entering it.
• When I type or paste a number or formula into a cell, sometimes it isn’t visible right away. I may have to hit save to see it, or click out of the spreadsheet, then back in. Or work a few more functions before it’ll show up in the cell. I can go to the cell and see it in the menu bar above, but the cell appears to be blank until the contents finally just appear. In addition, if I'm changing the formula in a cell that affects other cells, instead of the changes to the other cells showing immediately, they may not show until I either hit save or scroll until the cells that should change are off the screen.
• Sometimes a cell picks up a format from an earlier cell, despite the fact that I have deselected “Extend data range formats and formulas”.

I've already done a full Office uninstall, including wiping all of the associated files, then reinstalling. It seems to me that my Office software is corrupt, but I don't know if that's the case, nor how to go about trying to get it replaced.

I'd appreciate any help or wisdom.

Thanks.