Phantom folders and files in C:\Windows\Temp

I recently started getting strange folders in Windows 10 Pro Temp on a laptop. Names all start with tmp which is followed by 8 characters, including letters, numbers and _. They are all marked "Read Only," which I'm unable to change. Although I have full control of the Temp folder and everything in it, I can't even open these folders to see what's in them. From what I can see, they aren't taking up any space on the drive. There are now 83 of them in addition to 5 zero-size mat-debug-xxxx.log files that I see inside Windows, but none of them are visible when I run Command Prompt on a rescue USB drive from outside. I ran PowerShell command Remove-Item C:\Windows\Temp\* -Recurse -Force, but was warned for each folder that I had no access. When I try to check for folder owner, I don't even have permission to do that. Full and offline scans by Defender showed no threats.

Any ideas? I'm unable to find much helpful info online. Suggestions there either won't work or don't apply since the laptop doesn't have installed drivers or programs identified as possible culprits. There is some mention that Windows updates could be at fault, but no indication whether it may be the updates themselves or faulty installation. I do still have a good backup from before the last 2 CUs, so could try that. 2 Windows 10 Pro desktops have the same Windows updates as the laptop and have no problems.

Hearsepilot said:

You should be able to delete any of these files that are not currently in use. As a test I've just checked my \appdata\temp folder and had 211 items and was able to delete all but 20 references. In Windows\Temp i had 176 references and could delete all but 2

I realize I should be able to delete them, but can't. I can delete some other files in Windows\Temp, but not these. There is no indication they are in use, only that I have no permission to delete or even open them. This is in spite of the fact that I have full control in the Windows\Temp folder.

Hearsepilot said:

Have you tried within safe mode?

Yes, tried in Safe Mode, but would have been surprised if that had worked since they couldn't be deleted from outside Windows. Also, I ran sfc /scannow and the DISM routine including RestoreHealth. I did find that some, but not all, the folders could be deleted by setting them one at a time to enable inheritance. About half of them refused to open the window for resetting. I may be onto something, though. After restoring an old (3-13) Macrium backup, the Windows\Temp folder was empty. It stayed that way until I updated some programs with Winget. After that, there were a couple dozen stubborn folders in Windows\Temp. I hadn't applied any Windows updates yet. That seems to be strong evidence that a program is causing all those folders to pop up. I restored the backup again and will update programs slowly and one at a time (not through Winget) while keeping a close eye on Windows\Temp. Maybe that will pinpoint the culprit. I'll hold off on marking this solved until I corner a suspect.