Corruption of Word documents

[Amelia43]

I am running Microsoft 365 Apps for Enterprise. Problems began around the time I upgraded Windows 10 Education to version 2004- the timing may be purely coincidental.
New Word documents often open with the whole page black, and I need to do an online repair to get back to a usable form of Word.
In addition, Word docs often will not close using the usual method of clicking the x in the upper right hand corner. I have to use Task manager to close Word.
Copy/paste to Word often fails, with the paste icon greyed out.
Word add-ons are those I have used for years, are are the most recent versions.
Very occasionally Excel sheets will not close, requiring Task Manager as well.
I find myself needing to do online repairs at least once a day, and am unable to isolate the problem.
Any suggestions will be gratefully received!

[HansV]

That's very annoying!

Do you save your documents on a local hard disk, or in the cloud (OneDrive)?

[Amelia43]

Thank you for replying, Hans. I save to the local hard drive, which has plenty of capacity and is healthy.

[HansV]

Thanks, that rules out one cause.

Have you tried repairing your Office installation (from Start > Settings > Apps)?

[Amelia43]

No I haven't used that method. I have been using Control Panel-Programs and Features etc. Quick repair does not help, and I need to do an online repair. I will try the alternative technique.
Thank you Hans. I will report back.

[Charles Kenyon]

Both procedures get you to the same place. If the Quick Repair does not work, yes, do the Online repair.

[Amelia43]

Thank you Charles- I thought that might be the case.

[JoeP]

What is the Office version? Which update channel are you in? Have you tried running Word with add-ins disabled?

[Amelia43]

Joe, it's version 2011 Build 13426.20308 Click-to-run. Updates are automatically downloaded and installed.
Yes, I tried disabling add-ons, and made sure that my antivirus software is not checking Office files.

[JoeP]

It seems to me that since you have the same problem repeated after multiple Office repairs, you either have a hardware problem or a corrupted Windows installation. A Windows 10 problem seems most likely.
Do you have IT support to help?

Have you tried a Windows reset?

Have you run any hardware diagnostics?

[Amelia43]

Thank you Joe. Your thoughtful responses are appreciated.
I will run hardware diagnostics again, and have been wary about a Windows reset- although, as you indicate, it may be necessary.
The timing of the onset of the MS 365 problem coincided with the Windows upgrade so the problem could well lie there.
Unsure about IT support- even though the software is provided by the university I work for, the hardware is my own personal machine- I will check with them.