Explorer.exe using large amounts of CPU until UEM explorer profile is cleared

[Justin_Y]

We have noticed this issue sporadically with different users. Explorer seems to max out a processor for no reason and it will persist with each logon until the explorer uem profile is reset. We were using UEM 9.2.1 and recently upgraded to 9.4. We saw it before the upgrade but I would guess any profiles we found it on were created in 9.2.1. Just checking if anyone has seen the issue and if they resolved it in there environment.

[Justin_Y]

I think we found the fix. On the machines that are having the issue if we delete the following key the Explorer process stops hogging a CPU. We are going to exclude this key from UEM to prevent users from having this issue or at least prevent it from persisting after a logoff.

[HKEY_CURRENT_USER\Software\Classes\Local Settings\Software\Microsoft\Windows\Shell\BagMRU]

"MRUListEx"

[HBRM]

Hello,

I take 5 mins to thank you because I think we had the same behaviour.

Less thant 10 users on 300 but the issue was following the deletion of their persistent VM.

I added an exclusion for the registry zone you mentionned and now, changing the vm resolve this painful issue.

Regards,

Hervé

[CoreyN]

I've also been seeing constant, high CPU usage from the explorer process randomly across users with UEM 9.6 with the built-in config template.  Once I add that exclusion everything is fine.  Thanks a lot!

[Justin_Y · Accepted solution]

After a lot of testing and seeing this come up even after adding the registry exclusion I recently stumbled upon this on technet and it works in all of our tests.

Explorer.exe High CPU with redirected Desktop folder

We are rolling this out so we will see if removing the explorer exclusions reveals that this is two issues or just one but from our testing they will not be needed.

To summarize you should see this issue when you are using folder redirection. I could reproduce by opening explorer. Opening a folder on the redirected desktop then going anywhere else. Instant 50% of two CPU consumed by explorer.exe.

We could temporarily fix the issue by removing the MRUListEx registry entries. We actually also tried removing the set of MRUListEx entries on each key below on logoff but they are only temporary if the users are doing the same actions.

We are deploying the PS script from the article as a UEM (Now DEM) asynchronous logon task

powershell.exe -executionpolicy bypass (folder path)\Exploerfix.ps

Going to give this some time and monitor with Vrops before submitting to VMware as a bug.

[CoreyN]

I was seeing the exact same chain of events as you even after putting in the previous work around.  I looked at a few VMs today with constant, high CPU usage and in each one explorer.exe was still cruising along at 50-60% CPU.  I checked that registry location and the CLSID key was missing on each one.  As soon as I created a new key and tried to rename it, it would automatically create an empty CLSID key before I could finish the rename, and the CPU usage went back to normal.  I'm going to put a similar work around in to create the empty key if it doesn't exist until we (hopefully) hear more about what the root cause is and maybe a long-term fix.

Thanks for digging around on this one, Justin!