FROM MSDN
https://blogs.msdn.microsoft.com/dsnotes/2016/03/01/com-intermittent-error-800703fa-illegal-operation-attempted-on-a-registry-key/
Reason :
The event warning explains that when the profile was unloaded, the w3wp.exe process had a registry key descriptor for the profile hive for the user.
According to article kb947238, event 1530 occurs because Windows automatically closes any registry descriptor for a user profile that remains an open application. This causes error 800703fa.
Resolution :
Go to IIS Manager, select the application pool for the web application and click "Advanced Settings", change the value "Download User Profile" to "true"
Setting these values ββcauses IIS to load the user profile to authenticate the application pool.
TEMP (NOT FROM MSDN) Restart the application pool or run the iisreset command.
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