Seems its the same old issue is rearing its head that many Windows 10 users have encountered over the last several years. There are a number of threads on tenforums as well as many posted elsewhere on the web. Do a web search "save as freezes Windows 10" I have never run into this issue, but from what I read about all the suggestions, things like SFC, Clean Boot, and DISM have not worked.
Personally,I would cut to the chase and do a non-destructive repair reinstall of Windows. This tutorial is for Windows 10 but it applies to 11 also. Scroll down the article to
To Do a Repair Install of Windows 10 with an ISO file.
https://www.tenforums.com/tutorials/16397-repair-install-windows-10-place-upgrade.html
If you don't go that route, the only thing I can suggest is to look in event viewer to see if anything shows up there that might lead you in the right direction. But I will tell you this is a daunting task to filter through what is important to your specific issue.
What Is the Windows Event Viewer, and How Can I Use It?
If you are unfamiliar using the event viewer, you would be much better off doing the repair install and get it over with.