I’am currently working on a project where we want to AzureAD join some Windows 10 devices after we have deployed them with SCCM.
In our test the uninstall of the SCCM client failed – and it resulted in a error code 8018000a when AzureAD joining the device.
Is seems normal until after user sign in to AzureAD for the AzureAD domain join in the Windows OOBE.
The the error “Something went wrong” shows
It is because it is not possible to AzureAD join a device with the SCCM client installed.
Solutions:
Uninstall the SCCM client with this command “c:\windows\ccmsetup\ccmsetup.exe /uninstall”
Then run c:\windows\system32\sysprep\sysprep.exe /oobe
Now it is possible to AzureAD join the device.
Cloud First 
Hi Per,
I do not have SCCM in my situation, but the client got stuck with error 801800A anways. Turns out that the client got stuck in its enroll process.
This was solved by removing some registry keys, feel free to check out the solution: https://jocha.se/blog/tech/azure-ad-mdm-intune-error-8018000a