Symptoms: CPU usage will spike to 100% and will be mostly used by the service "Azure AD Connect Health Sync Monitoring Service".

Cause: .Net framework update before the software fully supports the underlying update.

Workaround: stopping the service will temporarily resolve the issue until the service restarts or the machine is restarted.

Fix is available from: https://www.microsoft.com/en-us/download/details.aspx?id=47594