Windows 10 1709 - wsappx process high cpu load & and black screen after login for some users

Updating to build 1803 seemed to fix it for all user accounts.

Our recent problem computers were all running 1803.

So I had the issues described above too: brand new Yoga520 with 1709 build OEM from Lenovo. I had created a first user (as a family parent) and then immediately continued to adding the children (before updating windows or rebooting etc.)

This got me a black screen after re-logon with the child account. The parent account was still fine. Tried everything until I decided to reset the machine. Did that and then made sure that I had updated windows with all recent fixes before continuing to create the child user again. I also rebooted the machine a few times, especialy from the 'Windows Update' button (instead of the regular 'start' button). Somehow, 'update and restart' from the start button didn't realy updated the machine. I also executed the above non-permanent fix. That didn't find any issues so I created the child user. Everything seemed to go smooth, I got the desktop, start menu was working so I guessed it was 'fixed'. BTW, I didn't remove any of the preloaded packages from lenovo nor did I go into regedit to change something.

Then I logged off and on again to the child account and ahhhh, there was the black screen again!!! Damn! The I logged on to the parent account and tried the fix again and hurray...i said it found and issue and fixed it! And indeed, now I could logon to the child account again without issues.

The machine is working fine for some days now...I lost a couple of days fixing this however but the above post helped me a lot! So I wanted to share my experiences too...

Thanks and good luck fixing...

Hmm, this sounds like my exact situation. If you don't remove the "My Office" app before installing your licensed Office, you end up with duplicate Office icons on the start menu (one of each that is unusable). And then things go downhill from there. I can't remember if the System Recovery image I downloaded from Dell to wipe and reinstall does not include this, but I don't remember having to go back and remove it on the reinstall. But then again, my memory is blurred by the many hours I've spent troubleshooting this issue.

Tried what you said, user could log in properly after but still seeing high cpu usage from wsaappx. Has that resolved this for you? 

*** EDIT - Seems like reinstalling the Windows Apps fixed this CPU issue afterwards. Looks like a fix, hopefully they get this resolved soon. I ran this: Get-AppXPackage | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}

For those who do not have another user, here is one solution. 

(Got some specific symptoms that I couldn't find help for yet, so maybe this will address someone's situation and be of some help) I have a Lenovo Laptop, with originally one user account. black screen only happens after login. Task manager works but freezes often, and other programs that I try to load often refuse to launch, namely control panel. 

From that black screen once you login, CTR+ALT+DLT and launch task manager. For me, control panel (control.exe) refused to launch when I ran it, for some reason. If it works for you, definitely go that route. If not:

run cmd from task manager. (be sure you run the task as admin)

Add a new user and add to admin group:

net user /add <username> <password>

net localgroup administrators <username> /add

that should work for creation of a new user, so restart your PC and that new account should be unaffected. You can then transfer your files and programs to your new account, and scrap the old one which is quite the ass-pain.

Or you can follow the steps that have been generously outlined earlier in the thread, to repair those service problems.