Can't edit scheduled tasks (MMC error)  

I'm running 20H2. Not long ago, I found I could no longer edit scheduled tasks. Tasks also run haphazardly (i.e. not at the correct time). If I open compmgmt.msc or taskschd.msc and either double click a task or right click one and select "Properties", I get an error:

MMC has detected an error in a snap-in and will unload it.
* Report this error to Microsoft, and then shut down MMC.
* Unload the snap-in and continue running

If I choose the "Unload" option mentioned above, a new window appears that mentions "FX:{c7b8fb06-bfe1-4c2e-9217-7a69a95bbac4} ... The system cannot find the file specified. (Exception from HRESULT: 0x80070002)". I've included screenshots as well.

I've run "sfc /scannow", and it reports that there are no file integrity violations.

I ran Sysinternals Process Monitor in an attempt to determine what file(s) are missing, and the only portion of the output that makes any sense to me is included in a screenshot.

Elsewhere on the internet, someone mentioned that files under "C:\Windows\assembly" may be missing or corrupt. I compared the contents of "C:\Windows assembly" to that from a backup I took about week prior, and there were files missing. I restored the files, rebooted, but the error persists.

There is no chance that I will do an in-place upgrade to fix this, because to me, that's like rebuilding your entire house to fix a clogged sink drain. Can someone please help with this?

The errors seen in MMC, when an attempt to edit a task is made:




Process Monitor output, created while the issue was being reproduced:

I didn't think that my PC specs had much to do with whether or not I could open tasks, especially since it's a recent issue. My PC is high-end and just over 1 year old.

I've been running 20H2 since shortly after it was released. This issue with scheduled tasks only started happening very recently.

I've used Hard Disk Sentinel Pro for years. My disk is fine.

"chkdsk c: /scan" comes back with:

Windows has scanned the file system and found no problems.
No further action is required.

964614143 KB total disk space.
297258540 KB in 303973 files.
248036 KB in 111935 indexes.
0 KB in bad sectors.
882539 KB in use by the system.
65536 KB occupied by the log file.
666225028 KB available on disk.

4096 bytes in each allocation unit.
241153535 total allocation units on disk.
166556257 allocation units available on disk.
Total duration: 14.48 seconds (14486 ms).

I managed to correct this. I think the problem was caused by installing a trial of VueMinder Pro, because the problem started immediately after that software was removed.

I monitor installations with Total Uninstall, but unfortunately, I had changes to C:\Windows\assembly excluded in Total Uninstall, so I wasn't aware that VueMinder Pro had made changes there.

Anyway, I found several files/directories under C:\Windows\assembly that had been created at the exact day/time I installed VueMinder Pro, deleted them, rebooted, and the issue was gone. I have no clue why deleting files would solve a "missing file" problem, but I'll take it.